Signature can be copied, deleted and moved with Apple Preview

[CrisCros1984]

Hello to the community.

I have been using the digital signature option from Adobe Acrobat Reader (currently version 2023.003 on Mac) for years. Specifically, I use the tool under "Certificates -> Sign digitally -> Sign with a digital ID".

Now by coincidence I noticed something, because I can display the signed PDF yes also in the Apple standard app "Preview":

There I can not only move the signature box, but also delete or copy it. I can also add and remove pages, so I can put a digital signature under a completely different contract.

I would like to know if this is a known effect (or even bug) and how I can prevent it with Adobe Reader.

Thank you and best regards

[Bernd Alheit]

Verify the signature in Acrobat Reader. 

[CrisCros1984]

Hi Bernd, 

thank you for your answer. If I understood you correctly, I should "verify" the signature on the signed document. If this fails, the signature is considered invalid.
Unfortunately, this does not solve my problem.

I would like to prevent my Adobe signature from being transferred to other documents using simple tools.

In the first moment these signatures then seem valid. That is often enough to gain trust.

So I ask why this is basically NOT moveable on Windows (as expected), but (surprisingly) quite easily moveable/changeable on Mac.

How can I avoid this?
Many greetings

[Bernd Alheit]

Does you mean the certificate or the visible signature?

[CrisCros1984]

Hi Bernd, 

it was done via "tools -> Certificates -> Digital Signature -> draw a rect -> select digital ID -> enter password"

I added some screenshots. 

Still not solved for me.

Best, Chris

[try67 · Accepted solution]

But if you copy that signature to another file, does it appear as just a graphic, or a real digital signature? If the latter, that is a huge security flaw. If the former, that is unfortunate (and should definitely be fixed by Apple), but more of an inconvenience, since the file is not really digitally signed.