Verify PDF signature
See who signed a PDF and whether it changed after signing. The file stays on this device.
Checking signatures…
Working on your device. Nothing is uploaded.
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A signature you can see on the page may be only a picture, and a picture cannot be checked. Only a digital signature shows who signed and whether the file changed.
Some changes at the end of the file are not covered by any signature.
- No uploadYour file stays on this device.
- Your original stays as it isYou download a new copy. Your file is never changed.
- Free, no sign-upNo account and no daily limit.
What happens to your file
Everything below happens inside your browser, on your own device. The PDF is never uploaded, so nobody else, including us, can see it.
- pdfMB finds each digital signature in the file and recalculates the fingerprint (hash) of the exact bytes it covers.
- It checks that fingerprint against the signature, using the public key in the signer’s certificate.
- It shows who the certificate belongs to, who issued it, and whether it was valid when the file was signed.
- It reports changes added after a signature, and lets you download the exact version that was signed.
- Choose a signed PDF
- Read the result for each signature
How to verify a PDF signature
- Choose the PDF. pdfMB checks every digital signature in it.
- Read the result for each signature: valid, not valid, or valid with changes added later.
- Check who signed and who issued their certificate. If the certificate is self-signed, anyone could have made it.
When people use it
Before you trust a signed document
Check that a contract, certificate or official letter has not been changed since it was signed.
After you sign
See what other people will see when they open the file you signed.
Several signers
See every signature in the file and which one came first.
What it can’t do
- pdfMB does not check lists of trusted authorities (such as Adobe’s or the EU’s) or whether a certificate has been revoked. Use Adobe Acrobat Reader or the EU signature validator for that.
- It checks digital signatures only. Pictures of signatures cannot be checked by anyone.
- It does not judge whether a change made after signing (such as filling in a form) was allowed by the signer.
- It does not say whether a signature is legally valid.
Questions about checking signatures
What does “valid” mean here?
The signed part of the file is exactly as it was when signed, and the signature matches the certificate shown. It does not prove that the person named in the certificate is who they say they are.
Why does it say “self-signed”?
The certificate was made by its owner rather than by a certificate authority. Anyone can make such a certificate with any name.
The file was changed after signing. Is the signature useless?
Not always. Filling in a form or adding another signature also adds changes. Download the version that was signed to see exactly what the signer signed.
Is my file uploaded?
No. The check runs in your browser, and the PDF never leaves your device.