Check a PDF's digital signature

Is this PDF still exactly as it was signed?

A digitally signed PDF, such as a signed contract or an official document, embeds the signature directly in the file, along with a byte range that marks exactly how much of the file the signature covers. If the document is edited after signing, even by adding a page or a stamp, that byte range no longer matches the current size of the file, a clear sign that something changed after the signature was applied. This tool checks for that.

What it checks

• Whether a signature is present at all, and how many if there is more than one.
• The signer's name, when it was included in the signature.
• Whether the file still matches what was signed, by comparing the signature's recorded byte range against the file's actual size.

What "modified after signing" means in practice

If the check reports that the file was changed after the last signature, it means bytes were added to the file following that signature: another signature, an edit, or something appended. It does not by itself say what changed or whether the change was legitimate, only that the file is no longer byte-for-byte what was signed.

What this is not

This is a structural check, not full cryptographic validation. It does not verify the signer's certificate against a trust chain, does not confirm the signature's cryptographic validity, and does not check for certificate revocation, the checks a dedicated PDF reader with signature validation performs, such as Adobe Acrobat. For a document where signature validity has legal weight, verify it with proper signature-validation software, not with this tool alone.

Privacy

The file is read entirely in your browser and is never uploaded.