Can AI tell if a PDF has been edited?

The useful part

This question is worth asking, but a confident AI answer can be misleading. AI is useful for structuring checks and comparing known versions. It is not enough for proving an unsigned PDF was or was not edited.

Adobe guidance on validating signatures provides the basis for the key limitation in this guide. This percentage is our editorial estimate of what AI can reliably handle on its own for this question, not measured accuracy or a probability that an answer is true.

Before you start

Define the decision you need to make and gather the best source material you can access. Remove unnecessary private information before pasting anything into an AI chat. If a decision affects another person, keep the process fair and preserve the original evidence.

How to do it

1. Keep the original file untouched and record where it came from.
2. Check whether Acrobat reports a valid digital signature and changes after signing.
3. Compare with a trusted earlier copy if one exists.
4. Document uncertainty; seek expert review for consequential disputes.

Copy this prompt

Help me investigate whether AI can tell if a PDF has been edited in my specific situation. Do not give a final verdict yet.

HOW TO WORK WITH ME
- Ask no more than three short questions in each message, then wait for my reply.
- Keep observed facts, assumptions and open questions separate.
- Say what evidence you can actually inspect. Never claim to have opened a file, searched the web or used a product unless you did.
- Give a cautious conclusion with its limitations. Never invent confidence percentages.
- If another person's rights, reputation or safety may be affected, avoid accusations and recommend a fair human review.

START WITH ONLY THESE THREE QUESTIONS
1. What PDF do you need to check, and do you have the original?
2. Is it digitally signed, or is it an unsigned copy or screenshot?
3. What specific change are you concerned about?
Then stop and wait.

IN LATER ROUNDS
Ask about trusted source copies, certificate details, signature validity and version history. Distinguish a cryptographic signature from a picture of a handwritten signature.
Ask for the minimum material needed. Let me remove private or confidential information. If you lack the original file, links or browsing access, explain how I can run the check myself.

BEFORE ANALYSIS
Summarise the task and the evidence I provided as numbered items. Put assumptions and missing evidence in separate lists. Ask me to correct the summary. Wait for my confirmation.

AFTER CONFIRMATION
Produce a cautious comparison report: verified changes, possible differences and unknowns. For every substantive finding, say which supplied item or opened source supports it. Explain what a specialist tool could help me check, and what it cannot establish. Give me an ordered, practical next-step checklist.


USE THIS CHECK SEQUENCE
1. Keep the original file untouched and record where it came from.
2. Check whether Acrobat reports a valid digital signature and changes after signing.
3. Compare with a trusted earlier copy if one exists.
4. Document uncertainty; seek expert review for consequential disputes.
If a step is impossible because evidence or access is missing, mark it 'not checked' and tell me what I would need to complete it. Separate a tool's signal from your own interpretation. End by asking which unresolved point I want to investigate next.

IMPORTANT LIMIT
Do not claim tampering from metadata alone or accuse a person. For a consequential dispute, preserve the original and seek a qualified examiner.

Begin with the three starting questions only.

What you should get

You should get a cautious comparison report: verified changes, possible differences and unknowns. Each finding should point to a real source or to something you supplied, and unknowns should stay visible.

Where AI falls short

Metadata and visual artifacts are not conclusive proof that an unsigned PDF was changed. Do not claim tampering from metadata alone or accuse a person. For a consequential dispute, preserve the original and seek a qualified examiner.

When another tool helps

Adobe Acrobat Reader can support one part of the check. Review its current features, access and results before relying on it. Its output does not settle the whole question.