Error when digitally signing a pdf

[NintendoPlayer]

So I'm trying digital signing with preview PDFsharp Core 6.2.0 Preview 1 on a NET. 8 project. I get my certificate from the certificates store and sign the pdf. Everything goes well until I save the document. I get this error:

System.Security.Cryptography.CryptographicException: 'Provider could not perform the action since the context was acquired as silent.'

I don't know what really is the issue, any thoughts?

Thanks!

Here is the code:

// Some code designing my pdf

//After that I call this function to sign the pdf
pdfDocumentOutput = signPdfWithDigitalCertificatev2(pdfDocumentOutput)

//Then I save the pdf
pdfDocumentOutput .Save(newFullFileName); -> Here is the line that prompts the issue above.

private PdfSharp.Pdf.PdfDocument signPdfWithDigitalCertificatev2(PdfSharp.Pdf.PdfDocument pdfDocumentOutput)
{
//Here I select the correct certificate with native popup window
var store2 = new X509Store();//(StoreName.My, StoreLocation.LocalMachine);
store2.Open(OpenFlags.ReadOnly);
var selectedCertificate = X509Certificate2UI.SelectFromCollection(
store2.Certificates,
"Title",
"MSG",
X509SelectionFlag.SingleSelection);

int signatureWidth = 210;
int signatureHeight = 150;

//This code is almost the same from the samples on Github

var options = new DigitalSignatureOptions()
{
ContactInfo = "Me",
Location = "Spain",
Reason = "I'm the authos",
Rectangle = new XRect(pdfDocumentOutput.Pages[0].Width / 2 - signatureWidth / 2, 750, signatureWidth, signatureHeight),
AppearanceHandler = new SignatureAppearanceHandler()
};

// I sign the pdf with the certificate I selected
var pdfSignatureHandler = DigitalSignatureHandler.ForDocument(pdfDocumentOutput,
new PdfSharpDefaultSigner(selectedCertificate[0], PdfMessageDigestType.SHA256, true ? new Uri("http://timestamp.apple.com/ts01") : null),
options);
return pdfDocumentOutput;
}

[ThomasHoevel]

Would be good to have some code to replicate the issue.

The document is signed after it was saved, so that's the time when the certificate is actually used.

The exception does not come from PDFsharp, so maybe you can find an answer on the Internet.

[NintendoPlayer]

Updated the my first post with code.

[NintendoPlayer]

Hi! Sorry, I was reading your answer again. How is that "The document is signed after it was saved"? I sign the pdf with the certificate and then call .Save(). That's when the exception arises. I'm using the suggested code on your docs page