We have a few problematic PDF files which the Adobe Reader opens without any error but when we attach them with PDFBox 1.8.12 to any other PDF and try to sign the file with the attachment, it throws an exception and the signing fails.
The thrown exception is:
org.apache.pdfbox.exceptions.SignatureException: The PDF file has no pages
If we use PDFBox 2.0.2 to attach, the signing succeeds.
Unfortunately we cannot publish the PDFs, they have confidential informations.