How to verify an electronically signed document

Why verify a signature

When you receive a signed document, three questions arise:

1. Whosigned?
2. Was the documentmodifiedafter signing?
3. Is thedateentered reliable?

Checking the signature brings the answer in 30 seconds.

Method 1: Adobe Acrobat Reader

The simplest. Adobe Reader automatically checks signatures in PAdES format.

1. Open the PDF in Adobe Reader
2. A banner at the top indicates "Valid signature" (green) or "Invalid signature" (red)
3. Click on the "Signatures" panel on the left for details
4. See: name of the signatory, date, certificate, service provider

If the banner says "At least one signature has problems", open properties for diagnosis.

Method 2: online tools

• DSS Demonstration WebApp(official ETSI tool): checks advanced and qualified signatures
• Signature Validatorfrom the European Commission
• pdfsig(command line, for IT)

Method 3: the issuing platform

If you know the signing platform, connect to your space to access the complete audit trail:

• precise date and time
• IP of the signatory
• OTP entered
• cryptographic fingerprint

The validity indicators

Indicator | Meaning

✅ Green “Valid signature” | Authenticity and integrity confirmed

⚠️ Yellow “Validity unknown” | Unrecognized certificate but correct signature

❌ Red “Invalid signature” | Altered document or corrupted signature

🕐 “Qualified timestamp” | Date proven by a QTSP

If the signature is invalid

Possible causes:

• document modified after signature
• expired or revoked certificate
• service provider not recognized by the reader
• corrupted file

In this case, contact the issuing platform for clarification.

Verify an AES signature

For an AES, the PDF contains the cryptographic signature + a pointer to the platform's audit trail. Check both:

• signature in the PDF (Adobe Reader)
• audit trail on the issuer side

Use case: verification during an audit

An auditor receives 50 electronically signed contracts to audit. Procedure:

1. Opening each PDF in Adobe Reader → status check
2. Consistency check (date, signatory)
3. Request for the audit trail from the platform for sample
4. SHA-256 fingerprint verification by comparison

Audit completed in 2 hours vs. 2 days on paper.

How Certyneo helps you

Certyneo allows any recipient of a signed document to verify:

• automatically via Adobe Reader (PAdES format)
• via a public verification link (shared by the issuer)
• via the API for integrations

The audit trail is exportable in PDF or JSON for external controls.

Discover the Certyneo electronic signature solution

FAQ

How long does verification take?

< 1 minute in Adobe Reader.

Without Adobe Reader, what to do?

Free online tools exist (ETSI DSS, EU Signature Validator).

Does the signature remain valid if we reprint the PDF?

The cryptographic signature remains in the PDF. A paper printout loses its probative value.

Can we verify a 10 year old signature?

Yes, for PAdES-LTA formats. More basic formats can be problematic with outdated algorithms.

Does the recipient have access to the audit trail?

Often yes, via a public link shared by the issuer.

Conclusion

Verifying an electronic signature takes less than a minute with Adobe Reader. This is an essential step to integrate into your audit and validation processes.

Try Certyneo to send, sign and track your documents online simply, quickly and securely.