How to append a new page(apostille)to a digitally signed PDF without invalidating original signature

Question

Hello,we have a legal-administrative workflow where:A PDF decision is generated and digitally signed (QES) by the head of department.After the legal deadline (e.g. appeal period), an apostille page (legal force confirmation) is added and signed by a second person.We understand that modifying a signed PDF normally invalidates the original signature. This is what happens when we try to add a new page using tools like Aspose or standard PDF editors.However, we have an official document that behaves differently:It has two valid digital signatures.The second signature (apostille) was added 14 days after the first.A new page (the apostille page) is clearly appended after the original document.Adobe Acrobat shows this as two revisions, and both signatures remain valid.Our question is: How is this kind of document technically created?Is there a specific process in Adobe Acrobat Pro, or through Adobe SDK/API, that allows you to append content in a way that creates a new revision (preserving the previous signature)?Is it necessary to use incremental updates or PDF signature certification options?We are attaching a redacted sample for demonstration.We'd appreciate any technical explanation or guidance on best practices for this kind of document handling.Thank you very much! link to sample

try67 · Accepted Answer

Impossible. You can't edit a signed document without invalidating its signature.

What you can do, though, is combine them both under a Portfolio, which is a kind of "envelope" file that contains other files as attachments. Or you can clear the signature, merge the files, then sign the merged file.

MikelKlink · Answer

Having discussed how what you describe might have been done, I now had the time to analyze your sample.pdf. As it turns out, one of your assumptions is wrong:

However, we have an official document that behaves differently:
It has two valid digital signatures.
The second signature (apostille) was added 14 days after the first.
A new page (the apostille page) is clearly appended after the original document.
Adobe Acrobat shows this as two revisions, and both signatures remain valid.

No, already the first document revision in your file has an empty second page, so no "new page has been appended after the original dopcument", the second page was there all along.

In the second document revision a signature has been added with a visualization on the first page.

In the third document revision another signature has been added with a visualization on the second page.

Thus, nothing extraordinary happened here, merely two signatures (each with its own appearance) have been added with some time going by inbetween.

Beware, a number of empty text fields also are present in the document which may serve (by fill-in) to add more content to the document.

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