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3 replies

try67
Community Expert
Community Expert
October 6, 2022

There is an entire science behind this kind of thing, called forensic document analysis, but it's not a trivial task. You will need some advanced (and often expensive) tools to be able to detect such things. PDF files can contain a sort of "cache" of previous versions of themselves, or a record of revisions done to them, so in theory it's possible to detect that a file has been modified after its initial creation, but it depends on many factors.

Legend
October 6, 2022

Are you hoping to detect whether the file was modified BEFORE you got it? No hope of that at all, unless it was signed by someone else. 

Legend
October 6, 2022

You must apply a digital signature using a certificate you own. Acrobat can detect whether the file has been modified since you created it (because any change does not match the certificate).

Participant
October 6, 2022

The pdf files are not created by me, they are created by others!! How can I apply a digital signature?