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I seem to remember that you could amend a signed PDF and add stuff to add a white rectangle over something you want to change (e.g. a pass/fail entry) and then
by arethuza 8y ago
I seem to remember that you could amend a signed PDF and add stuff to add a white rectangle over something you want to change (e.g. a pass/fail entry) and then stick in the new text over the rectangle.
The original text was there, and hadn't been modified so the signature was still valid, but the superficial appearance of the document was misleading even if it was possible to identify the tampering if you knew what to do (which I suspect 99.9% of people reading PDFs would never bother doing).
- rauhl 8y agoYeah, that would be bad — hence my proviso ‘so long as it’s clear what [the post-signature modifications] are.’ If modifications aren’t clearly called out, then that’s a (bad) bug in the viewer.
- arethuza 8y agoI think that's where certification was supposed to come in (its been 10+ years since I worked with this stuff so my recollection is a bit vague) - you create the main structure of the document and then lock that down with certification and allow people to complete existing fields, including adding signatures.