Verify PDF Signature – Free, No Upload

How to check the signatures in a PDF

Add your PDF
Drop it above or choose it.
Read the report
Each signature is listed with its signer, its time and whether the signed bytes are unchanged.
Keep it in mind
The report tells you what the file says. It does not tell you who to trust.

What stays and what doesn't

Checking writes no file. The report says what was checked and what was not:

When it won't run

Five things stop a run before it writes anything, and each is said on the file's row. A PDF that needs a password asks for it there, and a wrong password is refused with a sentence that says so. A digitally signed PDF is held back until you choose to continue, because checking it would break the signature. A file that cannot be read is reported as damaged. A job too large for this device says so, and in every case nothing is changed and your original stays as it was.

Checking a signature: what to expect

A digital signature covers the bytes of the file up to a point. The check hashes those bytes again and compares them with what was signed, so it can tell you whether they have changed. It also lists the certificates the signature carries and the time it claims.

It does not decide whether the signer is who they claim to be. Anyone can make a certificate with any name, and this check does not ask a list of trusted authorities or the network. Whether to trust a signer is your call.

A signature that leaves part of the file outside what it covers is not called unchanged: the report says part of the file is not covered. If the file was added to after it was signed, the report says so, because a later signature, a filled field and a changed page look alike from outside.

Whether a certificate was withdrawn is not looked up, because that needs the network. Signatures made with methods the browser cannot check are listed as something it cannot check.

Questions

Are my PDFs uploaded?

No. Your PDFs are processed inside your browser, on your own phone or computer, and saved straight from this page. The reading at the top of the page counts every byte sent, and it stays at 0 B.

Does it tell me a signature is trusted?

No. It tells you what the file says and whether the signed part changed. Trust is your decision.

Does it use the internet?

No. The whole check is made in your browser, and nothing is looked up.

What if the file was changed after signing?

If the signed part changed, the report says so. If the file only has more in it than the signature covers, the report says that instead.

Can it check a drawn signature?

No. A drawn or typed signature is only a picture on the page, and nothing in it can be checked.

What does a self-signed certificate mean?

The signer made the certificate for themselves. The signature can still show whether the file changed, but nothing says the name on it is real.

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