Disabling editing of applied stamps in Reader

[korax1989]

After applying several stamps to a document, I am signing it with a commercial certificate. Even after applying the signature, the stamps can still be moved around and edited. Is there any reliable and user-friendly way to prevent this? I do not consider additionally restricting editing reliable not user-friendly. Is there any other option?

Why I'm asking: we are using commercial digital signatures to sign documents - contracts and such. Sometimes we also need to add not just the signature graphical representation (its scan), but also to add the date or name of the signing person. Although this is possible to include in the signature, it is practically impossible to edit the formatting of this information, which means that its layout is based on what kind of rectangle the user draws for the signature. This often means that using the signature this way involves many attempts before it looks good. Therefore, we would like to only use the signature with the sign image, and to add the extra information using stamps. On the other hand, these should be impossible to edit after the document is signed or saved. 

We are using Acrobat Reader DC and I have the full version of Acrobat as the only one in the company.

[try67 · Accepted solution]

Tick the "Lock document" check-box in the Signature dialog.

[korax1989]

Ah! That's excellent! And a bit obvious, I could have figured it out... many thanks, I appreciate the advice 😊

[MikelKlink]

While locking indeed is the best answer to give in this context in general, this is a feature introduced with PDF 2.0 (ISO 32000-2) and before used by Adobe Acrobat as an Adobe extension to PDF 1.7 (ISO 32000-1).

So please be aware that there is a lot of PDF processing software out there that only supports plain ISO 32000-1. Such software will not recognize the lock you introduced and, therefore, will allow editing your stamp and not consider changes to the stamp as invalidating the signature.

[Test Screen Name]

Yes, you should bear in mind that a lot of software will ignore any and all security features (except an Open password). You CANNOT protect your contracts by making files "uneditable". And even if you could; it would take seconds to create a new fake copy of any contract. Be aware and don't trust anything.

DIGITAL signatures with a paid for certificate CAN be considered safe; the file can be edited still but the changes can always be detected. The trick is to understand that the signature on the page - the visible thing - is of no value at all, because it can be faked in seconds. Only the signature PANEL is useful.

[korax1989]

I absolutely understand that it's not the signature graphic that protects the document, but instead it is the encryption applied to the document when applying the signature. 

And although I do understand that this method is not bullet proof, it is a sufficient barrier, mainly considering the fact that the signature would be invalidated in case someone would temper with the document. That being said, if there were a more secure method to do this that would be doable without forcing our top management to go into detailed settings of acrobat, etc., I am keen to hear about it.