Validate Signature
Check the digital signatures on a PDF - signer identity, certificate details, validity dates and whether the document has been altered since signing.
Upload Signed PDF
About This Tool
A signature block on a page is a graphic. It can be copied, faked, or left over from a document that has since been modified. The only way to know whether a signature means anything is to verify it cryptographically.
This checks each signature in the document and reports what it finds: who signed, which certificate was used and by whom it was issued, the validity period, whether the certificate had expired at the time of signing, and whether the document has been altered since.
That last point is the one that matters most. Integrity checking is what distinguishes a real signature from a picture of one, and it is the check almost nobody performs.
How to Use
Add the signed PDFs
Drop in up to 10 files. Every signature in each is examined.
Read the report
Signer, certificate issuer, validity dates and integrity status are listed per signature.
Check for modifications
The report states whether the document has changed since it was signed.
Export if needed
Save the validation report as JSON for a compliance record.
Use Cases
Verifying a received contract
Confirm the signature is real and the document has not been altered since signing.
Compliance auditing
Batch-validate a set of signed records and keep the report as evidence.
Detecting tampering
Establish whether a document changed after it was signed.
Frequently Asked Questions
What does a valid signature actually tell me?
That the document has not changed since signing, and that the signature was produced with the private key belonging to that certificate.
Why might a signature show as invalid?
The document was modified after signing, the certificate had expired or been revoked, or the issuing authority is not trusted.
Can I validate several files at once?
Yes, up to 10 per run, with a report for each.
Does an expired certificate invalidate the signature?
Not necessarily. If a trusted timestamp shows the signature was made while the certificate was valid, it can still verify. The report shows both dates.