How to verify a digital signature in a pdf document
- Step 1Obtain the signed PDF — Download or receive the PDF with the digital signature.
- Step 2Upload to the signature viewer — Drop the PDF into the verification tool.
- Step 3Review the signature report — Read the validation result — valid signature, certificate status, and modification check.
- Step 4Accept or reject the document — Proceed with the document if the signature is valid, or request a new signed copy if invalid.
Frequently asked questions
What does 'signature valid but certificate unknown' mean?+
The signature is cryptographically intact but the signing certificate could not be verified against a trusted root. This is common with self-signed certificates.
Can this verify eIDAS-compliant qualified electronic signatures?+
The tool verifies standard X.509-based digital signatures. Qualified signature verification under eIDAS may require a dedicated trust service provider tool.
Will it detect if someone altered the PDF after signing?+
Yes — any modification to the signed content after signature creates a hash mismatch, which the tool reports as an invalid signature.
Privacy first
All PDF processing runs locally in your browser using PDF-lib and pdf.js. No file is ever uploaded — only metadata counters are saved for signed-in dashboard stats.