Unable to modify a protected PDF. Use the /pdf_owner_pass option to specify an owner password.

[LMUAVASIS]

We have a word file as cover page which will merged with a PDF document. This works fine. But if the PDF document has markups or forms we get the following error:

Unable to modify a protected PDF. Use the /pdf_owner_pass option to specify an owner password.

The PDF file itself has no protection. It works also with a PDF/A as long as there are no markups and forms in the PDF.

Any idea what we can do?

THX for any help.

Ludwig