When you open a PDF document with an electronic and graphic signature, the signature is invalidated

Idepato wrote:

If I open the document in Image preview, I can move the Graphic Signature that is linked to the electronic signature in the PDF document. Once I move it, I don't even have to save the document and the electronic signature is invalidated. Nowhere does it do it like this like with Image preview, so I am writing here for advice. Maybe you can advise me not to open PDF documents with an electronic signature in Image preview, but I need to know the answer that why it does that.

Because any "properly designed" macOS/iOS apps automatically save the document any time you make a change. In many cases, even opening the document is sufficient to modify it. If you have a document that is signed, it would be best to lock it in the Finder to prevent modifications.

Note that this automating saving behaviour also includes version restore. So if this happens, you should be able to browse versions and restore valid version.

Alternatively, report a Bug.

That's your responsibility.

Preview just does not handle these kinds of things well, along with forms. I don't know that we can tell you *why*.

Whenever weirdness like this happens, switch to Acrobat.

Feel free to report this behavior to Apple:

Product Feedback - Apple

Preview does not attempt to run any Adobe Acrobat JavaScript (AcroJS) code in the PDF that may be controlling form settings, or potentially signature issues.

It has been a while, but I remember that I encountered a PDF a few years back that actually had embedded code expecting a particular Acrobat Plug-in presence as part of the normal PDF behavior. Preview wouldn't handle that request, and even Adobe Acrobat Reader would not do so if that Acrobat Pro plug-in was not installed.