When saving document in PdfA1b the signature doesn't appear write

When saving attached document in PDF with the option PdfA1b the signature in the document doesn’t appear write in the PDF-document.

Dim doc As New Aspose.Words.Document("c:\Aspose\RTF\" & bestand.Name)
Dim options As New Saving.PdfOptions()
options.Compliance = Saving.PdfCompliance.PdfA1b
doc.SaveToPdf(0, doc.PageCount, "c:\Aspose\PDF\" & bestand.Name & ".pdf", options)

Without the option PdfA1b the signature is okay in the PDF-document. How can we resolve this problem?

Hello
Thanks for your request. It seems your document contains transparent PNG image. And as far I know using of transparency is forbidden in PDF/A-1. Please see the following link:
https://en.wikipedia.org/wiki/PDF/A
As a workaround you can try using jpg type of image instead of png.
Best regards,