A PDF review can become confusing when several signatures and later changes are present. Begin by stating which point in the document's history you want to examine. The filename alone is not a useful description of that review boundary.

Use a supplied, authorised fictional sample with multiple signed revisions. Preserve it and record the sample filename plus the signature entries you intend to inspect. This exercise examines an existing document; it does not require adding another signature.

Select the comparison boundary

In Acrobat desktop, open Signatures from the right panel and select the relevant signature. Under Options, choose Compare Signed Version to Current Version. Review the information in the dialog and confirm with OK.

The selected signature determines the signed version being compared with the current document. Select an earlier signature and then a later one for two separate comparisons; record which entry was selected for each result.

Label observations so they can be reproduced

Prepare a review sheet with one row per selected signature. Include the visible identifying details, the question being investigated and the comparison observations. Keep the current file constant during this exercise so each row answers a clearly stated question.

For example, a reviewer might want to know whether a reference on the current page was already present at the first signing point. Write that as the question, then record only what the comparison actually demonstrates. If the report does not resolve it, keep the uncertainty rather than filling it with an assumption.

Ask a second reviewer to reproduce one row by selecting the same signature entry. If they chose a different entry, resolve that selection mismatch before debating the reported changes.

A useful result names both the selected signing point and the current file inspected. Keep this comparison record separate from any assessment of signer trust or legal validity. The presence of a visible signature mark is not, by itself, an answer to the revision question.

Sources: Adobe: signed revisions.