PDF Signature Viewer
Check the digital signatures in a PDF: who signed it, when, whether the document has been changed since, and the signer's certificate chain and timestamp. Works with PAdES, CAdES and PKCS#7 signatures, certification signatures and document timestamps. The PDF is checked in your browser and not uploaded.
What is the PDF Signature Viewer?
Contracts and official documents are often signed with a digital signature: a cryptographic signature embedded in the PDF together with the signer's certificate. This tool reads those signatures and checks them, so you can see who signed the PDF, when, and whether anything has been changed since. The PDF is read and checked in your browser. It is not uploaded anywhere.
How to use
- Drop a PDF onto the drop area, or click it to choose one.
- Each signature is shown with its result, the signer, the signing time, the reason and location, and the certificate chain.
- If content was added after a signature, click Download signed version to get the PDF exactly as it was when that signature was made.
Results
| Result | Meaning |
|---|---|
| Valid | The signature matches the signer's certificate, and the document has not been changed since it was signed. |
| Valid, changed after signing | The signature is valid for the signed version, but more content was added to the file afterwards (for example another signature, form filling or comments). The added content is not covered by this signature. |
| Invalid | The signed content has been changed, or the signature does not match the certificate. |
| Cannot check | The signature uses an algorithm or format that cannot be checked in the browser. |
| Not signed | An empty signature field. |
What is checked
- The hash of the signed part of the file (/ByteRange) against the hash in the signature
- The signature against the public key in the signer's certificate (RSA, RSA-PSS, ECDSA P-256/384/521 and Ed25519 where the browser supports it)
- That the signed part covers the whole file, or how many bytes were added afterwards
- Signature timestamps and document timestamps (RFC 3161): the time, the timestamp authority, and that the timestamp belongs to the signature
- The certificate chain: each certificate is checked against the certificate that issued it, as far as the certificates included in the PDF allow
- Whether the signer's certificate was valid at the time of signing
- Certification signatures (DocMDP) and the changes they allow
- Long-term validation (LTV) data embedded in the PDF
What is not checked
- Trust. Whether the root certificate belongs to a trusted authority is not checked. Adobe Acrobat uses its own trust lists for this. Look at the certificate chain and the fingerprints to decide whether you trust the signer.
- Revocation. Checking whether a certificate was revoked would mean contacting the certificate authority. This tool does not send anything, so it only reports whether revocation data is embedded.
FAQ
My PDF has a signature or a seal image, but no signature is found
An image of a handwritten signature or a seal is not a digital signature. Only signatures made with a certificate (for example by Adobe Acrobat, e-signature services or a signing card) are found.
Is my PDF uploaded?
No. The PDF is read in your browser. It is also kept in this browser so that it is still there the next time you open the tool. Turn off keeping files in the settings if you do not want that.
Why does Adobe Acrobat show a different result?
Acrobat also checks trust and revocation using its own lists and online checks. A signature can be valid here (unchanged and cryptographically correct) but shown as "validity unknown" in Acrobat because the signer is not on its trust list.