PDF Signed document - adding pages bricks existing Signature-Metadata-Information


Today i have successfully signed a PDF-Document as described in the documentation.

(Add digital signature or digitally sign PDF in C#|Aspose.PDF for .NET)

After that in a second step i reloaded the PDF-Document from the filesystem and added pages programmatically.


var attachDocumentPDF = new Aspose.Pdf.Document(tmpStream); sourcePDF.Pages.Add(attachDocumentPDF.Pages);

sourcePDF.Save(inMemorySourcePDF, Aspose.Pdf.SaveFormat.Pdf);

I know that the signature should be broken now (message like: Pages added after siging…)

But in my case the signature is not broken as expected, instead the signing information is now unreadable for PDF readers like Adobe-Acrobat-Reader(current version 2015.010.20056)!

The error message in Adobe-Reader:

(Support-Information: SigDict /Contents illegal data)

Its not possible to read any information about the signature now (like name, location or anything else) The message is: “Signed by unknown” - Signature invalid

I have attached the Adobe-Signature messagewindow (german version).

Best regards


Hi Johannes,

Thanks for your feedback. Yes you are right adding page will break the document security and invalidate(break) the signature as well. Please check following documentation link to extract signature details. Furthermore, you can validate signature using Aspose.Pdf and proceed accordingly. However if there is any difference in your requirements and my understanding then please share some more about the issue description, so we will guide you accordingly.

Best Regards,