diff --git a/lang/translations/ar.po b/lang/translations/ar.po
index 63eaa8d..4fde172 100644
--- a/lang/translations/ar.po
+++ b/lang/translations/ar.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Arabic (https://www.transifex.com/ckeditor/teams/11143/ar/)\n"
diff --git a/lang/translations/ast.po b/lang/translations/ast.po
index 9778794..0cecdc2 100644
--- a/lang/translations/ast.po
+++ b/lang/translations/ast.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Asturian (https://www.transifex.com/ckeditor/teams/11143/ast/)\n"
diff --git a/lang/translations/az.po b/lang/translations/az.po
index 12150d9..dda7258 100644
--- a/lang/translations/az.po
+++ b/lang/translations/az.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Azerbaijani (https://www.transifex.com/ckeditor/teams/11143/az/)\n"
diff --git a/lang/translations/cs.po b/lang/translations/cs.po
index 8a5e726..22ccec7 100644
--- a/lang/translations/cs.po
+++ b/lang/translations/cs.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Czech (https://www.transifex.com/ckeditor/teams/11143/cs/)\n"
diff --git a/lang/translations/da.po b/lang/translations/da.po
index 0349136..b08ef83 100644
--- a/lang/translations/da.po
+++ b/lang/translations/da.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Danish (https://www.transifex.com/ckeditor/teams/11143/da/)\n"
diff --git a/lang/translations/de.po b/lang/translations/de.po
index 1c0dfb8..679594c 100644
--- a/lang/translations/de.po
+++ b/lang/translations/de.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: German (https://www.transifex.com/ckeditor/teams/11143/de/)\n"
diff --git a/lang/translations/el.po b/lang/translations/el.po
index 7012bc6..516a3b6 100644
--- a/lang/translations/el.po
+++ b/lang/translations/el.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Greek (https://www.transifex.com/ckeditor/teams/11143/el/)\n"
diff --git a/lang/translations/en-au.po b/lang/translations/en-au.po
index b0856b0..7f078cd 100644
--- a/lang/translations/en-au.po
+++ b/lang/translations/en-au.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: English (Australia) (https://www.transifex.com/ckeditor/teams/11143/en_AU/)\n"
diff --git a/lang/translations/en.po b/lang/translations/en.po
index 76386bb..af90122 100644
--- a/lang/translations/en.po
+++ b/lang/translations/en.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language: \n"
diff --git a/lang/translations/eo.po b/lang/translations/eo.po
index 445c97d..551b924 100644
--- a/lang/translations/eo.po
+++ b/lang/translations/eo.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Esperanto (https://www.transifex.com/ckeditor/teams/11143/eo/)\n"
diff --git a/lang/translations/es.po b/lang/translations/es.po
index f69000c..d838f0f 100644
--- a/lang/translations/es.po
+++ b/lang/translations/es.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Spanish (https://www.transifex.com/ckeditor/teams/11143/es/)\n"
diff --git a/lang/translations/et.po b/lang/translations/et.po
index b1182e1..dbbcab3 100644
--- a/lang/translations/et.po
+++ b/lang/translations/et.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Estonian (https://www.transifex.com/ckeditor/teams/11143/et/)\n"
diff --git a/lang/translations/eu.po b/lang/translations/eu.po
index cd00c01..54e61e5 100644
--- a/lang/translations/eu.po
+++ b/lang/translations/eu.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Basque (https://www.transifex.com/ckeditor/teams/11143/eu/)\n"
diff --git a/lang/translations/fa.po b/lang/translations/fa.po
index f30d038..c7ad41a 100644
--- a/lang/translations/fa.po
+++ b/lang/translations/fa.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Persian (https://www.transifex.com/ckeditor/teams/11143/fa/)\n"
diff --git a/lang/translations/fi.po b/lang/translations/fi.po
index eb5a8f1..68a2a68 100644
--- a/lang/translations/fi.po
+++ b/lang/translations/fi.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Finnish (https://www.transifex.com/ckeditor/teams/11143/fi/)\n"
diff --git a/lang/translations/fr.po b/lang/translations/fr.po
index 3c18532..25eac3f 100644
--- a/lang/translations/fr.po
+++ b/lang/translations/fr.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: French (https://www.transifex.com/ckeditor/teams/11143/fr/)\n"
diff --git a/lang/translations/gl.po b/lang/translations/gl.po
index 22c26a2..792b56f 100644
--- a/lang/translations/gl.po
+++ b/lang/translations/gl.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Galician (https://www.transifex.com/ckeditor/teams/11143/gl/)\n"
diff --git a/lang/translations/he.po b/lang/translations/he.po
index 151ef6b..2b019f7 100644
--- a/lang/translations/he.po
+++ b/lang/translations/he.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Hebrew (https://www.transifex.com/ckeditor/teams/11143/he/)\n"
diff --git a/lang/translations/hr.po b/lang/translations/hr.po
index 0b38f01..079545d 100644
--- a/lang/translations/hr.po
+++ b/lang/translations/hr.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Croatian (https://www.transifex.com/ckeditor/teams/11143/hr/)\n"
diff --git a/lang/translations/hu.po b/lang/translations/hu.po
index 60c02a1..4a182a1 100644
--- a/lang/translations/hu.po
+++ b/lang/translations/hu.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Hungarian (https://www.transifex.com/ckeditor/teams/11143/hu/)\n"
diff --git a/lang/translations/id.po b/lang/translations/id.po
index fdf7e9d..be3b56f 100644
--- a/lang/translations/id.po
+++ b/lang/translations/id.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Indonesian (https://www.transifex.com/ckeditor/teams/11143/id/)\n"
diff --git a/lang/translations/it.po b/lang/translations/it.po
index 7e8162f..db5a338 100644
--- a/lang/translations/it.po
+++ b/lang/translations/it.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Italian (https://www.transifex.com/ckeditor/teams/11143/it/)\n"
diff --git a/lang/translations/ja.po b/lang/translations/ja.po
index 0d9a299..24a94da 100644
--- a/lang/translations/ja.po
+++ b/lang/translations/ja.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Japanese (https://www.transifex.com/ckeditor/teams/11143/ja/)\n"
diff --git a/lang/translations/km.po b/lang/translations/km.po
index a392021..b7a345e 100644
--- a/lang/translations/km.po
+++ b/lang/translations/km.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Khmer (https://www.transifex.com/ckeditor/teams/11143/km/)\n"
diff --git a/lang/translations/kn.po b/lang/translations/kn.po
index 5b5a718..7f2ce39 100644
--- a/lang/translations/kn.po
+++ b/lang/translations/kn.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Kannada (https://www.transifex.com/ckeditor/teams/11143/kn/)\n"
diff --git a/lang/translations/ko.po b/lang/translations/ko.po
index 445b020..b4d6c97 100644
--- a/lang/translations/ko.po
+++ b/lang/translations/ko.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Korean (https://www.transifex.com/ckeditor/teams/11143/ko/)\n"
diff --git a/lang/translations/ku.po b/lang/translations/ku.po
index b7afa38..11d9e18 100644
--- a/lang/translations/ku.po
+++ b/lang/translations/ku.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Kurdish (https://www.transifex.com/ckeditor/teams/11143/ku/)\n"
diff --git a/lang/translations/nb.po b/lang/translations/nb.po
index 1889427..8264508 100644
--- a/lang/translations/nb.po
+++ b/lang/translations/nb.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Norwegian Bokmål (https://www.transifex.com/ckeditor/teams/11143/nb/)\n"
diff --git a/lang/translations/ne.po b/lang/translations/ne.po
index 81f2051..814445f 100644
--- a/lang/translations/ne.po
+++ b/lang/translations/ne.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Nepali (Nepal) (https://www.transifex.com/ckeditor/teams/11143/ne_NP/)\n"
diff --git a/lang/translations/nl.po b/lang/translations/nl.po
index 7c3dadf..b0d2e27 100644
--- a/lang/translations/nl.po
+++ b/lang/translations/nl.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Dutch (https://www.transifex.com/ckeditor/teams/11143/nl/)\n"
diff --git a/lang/translations/no.po b/lang/translations/no.po
index de53d7b..2fd97e7 100644
--- a/lang/translations/no.po
+++ b/lang/translations/no.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Norwegian (https://www.transifex.com/ckeditor/teams/11143/no/)\n"
diff --git a/lang/translations/pl.po b/lang/translations/pl.po
index 13fb6c7..1fb50e0 100644
--- a/lang/translations/pl.po
+++ b/lang/translations/pl.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Polish (https://www.transifex.com/ckeditor/teams/11143/pl/)\n"
diff --git a/lang/translations/pt-br.po b/lang/translations/pt-br.po
index d771b5d..59c1679 100644
--- a/lang/translations/pt-br.po
+++ b/lang/translations/pt-br.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Portuguese (Brazil) (https://www.transifex.com/ckeditor/teams/11143/pt_BR/)\n"
diff --git a/lang/translations/pt.po b/lang/translations/pt.po
index 90bfef8..07facbd 100644
--- a/lang/translations/pt.po
+++ b/lang/translations/pt.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Portuguese (https://www.transifex.com/ckeditor/teams/11143/pt/)\n"
diff --git a/lang/translations/ro.po b/lang/translations/ro.po
index 91f7556..892099b 100644
--- a/lang/translations/ro.po
+++ b/lang/translations/ro.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Romanian (https://www.transifex.com/ckeditor/teams/11143/ro/)\n"
diff --git a/lang/translations/ru.po b/lang/translations/ru.po
index df5ff03..e35f690 100644
--- a/lang/translations/ru.po
+++ b/lang/translations/ru.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Russian (https://www.transifex.com/ckeditor/teams/11143/ru/)\n"
diff --git a/lang/translations/sk.po b/lang/translations/sk.po
index b931823..e756687 100644
--- a/lang/translations/sk.po
+++ b/lang/translations/sk.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Slovak (https://www.transifex.com/ckeditor/teams/11143/sk/)\n"
diff --git a/lang/translations/sq.po b/lang/translations/sq.po
index 62d01db..312ca0b 100644
--- a/lang/translations/sq.po
+++ b/lang/translations/sq.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Albanian (https://www.transifex.com/ckeditor/teams/11143/sq/)\n"
diff --git a/lang/translations/sv.po b/lang/translations/sv.po
index e00df64..4739182 100644
--- a/lang/translations/sv.po
+++ b/lang/translations/sv.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Swedish (https://www.transifex.com/ckeditor/teams/11143/sv/)\n"
diff --git a/lang/translations/tr.po b/lang/translations/tr.po
index da3f7f6..72be54d 100644
--- a/lang/translations/tr.po
+++ b/lang/translations/tr.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Turkish (https://www.transifex.com/ckeditor/teams/11143/tr/)\n"
diff --git a/lang/translations/ug.po b/lang/translations/ug.po
index 8ad6f02..3e56edd 100644
--- a/lang/translations/ug.po
+++ b/lang/translations/ug.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Uighur (https://www.transifex.com/ckeditor/teams/11143/ug/)\n"
diff --git a/lang/translations/uk.po b/lang/translations/uk.po
index 706ddc4..7792584 100644
--- a/lang/translations/uk.po
+++ b/lang/translations/uk.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Ukrainian (https://www.transifex.com/ckeditor/teams/11143/uk/)\n"
diff --git a/lang/translations/vi.po b/lang/translations/vi.po
index 4fb625a..3b3d6a0 100644
--- a/lang/translations/vi.po
+++ b/lang/translations/vi.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Vietnamese (https://www.transifex.com/ckeditor/teams/11143/vi/)\n"
diff --git a/lang/translations/zh-cn.po b/lang/translations/zh-cn.po
index c1af7fe..2bf4207 100644
--- a/lang/translations/zh-cn.po
+++ b/lang/translations/zh-cn.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Chinese (China) (https://www.transifex.com/ckeditor/teams/11143/zh_CN/)\n"
diff --git a/lang/translations/zh.po b/lang/translations/zh.po
index b56a6ab..ec35a9b 100644
--- a/lang/translations/zh.po
+++ b/lang/translations/zh.po
@@ -1,4 +1,15 @@
 # Copyright (c) 2003-2019, CKSource - Frederico Knabben. All rights reserved.
+#
+#                                     !!! IMPORTANT !!!
+#
+#         Before you edit this file, please keep in mind that contributing to the project
+#                translations is possible ONLY via the Transifex online service.
+#
+#         To submit your translations, visit https://www.transifex.com/ckeditor/ckeditor5.
+#
+#                   To learn more, check out the official contributor's guide:
+#     https://ckeditor.com/docs/ckeditor5/latest/framework/guides/contributing/contributing.html
+#
 msgid ""
 msgstr ""
 "Language-Team: Chinese (Taiwan) (https://www.transifex.com/ckeditor/teams/11143/zh_TW/)\n"