PDF Signature Inspector

This tool reads the digital signatures in a PDF and shows the signer and certificate details stored in them. It does not verify a signature: it does not check that the document is unchanged since signing, that the signature value is correct, or that the certificate chains to a trusted authority. "Signature found" means only that a signature was read.

For each signature it shows:

• the name, organisation and email address in the first certificate inside the signature, which is usually, though not always, the signer's
• the issuer, the validity dates, the serial number and the algorithm identifiers, under Technical Details
• the signing time, reason and location written by the signing software; the time comes from the signer's computer
• Full Coverage or Partial Coverage: whether the signed byte range reaches the end of the file. Partial means data was added after signing, which can be a later signature or an edit; the tool cannot tell which.
• Certificate Expired or Self-Signed Certificate warnings. Expiry is judged against today's date, not the signing date.

You can also load a certificate file (.pem, .crt, .cer or .der) as a reference. A signature is then marked Trusted when that certificate issued one of the certificates in the signature, or has the same serial number as one of them. That is a quick match, not a cryptographic chain check. The "valid" count in the summary means read and not expired, nothing more.

To verify a signature, open the file in a PDF reader with signature validation, or use a validation service when a qualified signature is involved. Signatures are found by searching the file's raw content, so one stored in a compressed object stream can be missed. The file is read locally and stays on your device. Background reading: electronic vs digital signatures in PDFs. To sign a file yourself, see Digital Signature.