Check whether a PDF changed
Drop a file to get its SHA-256 fingerprint. Paste the fingerprint the sender gave you, or drop the copy you already had, and you will know whether the two are the same file, byte for byte.
The page also reads what a PDF says about itself: which program saved it, when it was created and modified, and how many times changes were appended to it.
A matching fingerprint means the same file, not a genuine one: it says nothing about who made it. The other findings are reasons to ask for the original, not proof of tampering. Banks and tax software produce PDFs with many programs.
Reviewed:
The files never leave this device: nothing is sent or saved, and reloading clears them.