Inspect digital signatures, ByteRange integrity, certificates, and signer metadata inside PDF documents locally.
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About PDF Signature Checker
Inspect the digital signatures inside a PDF: signer name, reason, location, signing time, signature type (SubFilter), ByteRange coverage and the certificates embedded in the PKCS#7/CMS data. It hashes the signed byte ranges and compares the digest with the signature's messageDigest, and reports bytes appended after signing (incremental updates). It does not check the certificate trust chain or the cryptographic signature value. The file is read locally and never uploaded.
Common uses
- See who signed a contract or invoice and when, without uploading it
- Check whether a signed PDF was modified after the signature was applied
- Inspect the certificate issuer, validity dates and algorithms of a signature
- Find out how many signatures and revisions a document has
FAQ
- What is the ByteRange in a PDF signature?
- ByteRange lists the parts of the file covered by the signature: everything except the /Contents value that holds the signature itself. If the ranges do not reach the end of the file, data was appended after signing.
- Does this tool prove a signature is valid?
- No. It checks that the signed bytes match the digest stored in the signature and shows the certificates, but it does not verify the signature value or whether the certificate chains to a trusted authority. Use a full validator such as Adobe Acrobat for that.
- Is it a problem if bytes were added after signing?
- Not necessarily. PDFs are often updated incrementally, for example to add a second signature or form data. It does mean the latest content is not fully covered by the earlier signature, so check what changed.