Adding Watermark to Signed PDFs

[Vonnie_Feng]

I have an extensive number of digitally signed PDFs. My organization want to add a watermark to those files without altering the content or removing the signatures. We also prefer to leave the original text in the PDF searchable.  How can I do that?

[try67]

You can't. A digital signature locks the file from further changes.

[Test Screen Name]

And... if you found software that ignored the lock, it would break the signature. This is how signatures are designed, so a file can't be edited after signing. For you, watermarks are innocuous but the PDF rules don't make allowance for it.