How to verify an electronically signed document

Why verify a signature

When you receive a signed document, three questions arise:

• Who signed it?

• Has the document been modified after signing?

• Is the date shown reliable?

Verifying the signature answers these questions in 30 seconds.

Method 1: Adobe Acrobat Reader

The simplest approach. Adobe Reader automatically verifies signatures in PAdES format.

• Open the PDF in Adobe Reader

• A banner at the top indicates "Valid Signature" (green) or "Invalid Signature" (red)

• Click on the "Signatures" panel on the left for details

• See: signer name, date, certificate, service provider

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

Method 2: Online tools

• DSS Demonstration WebApp (official ETSI tool): verifies advanced and qualified signatures

• Signature Validator from the European Commission

• pdfsig (command line, for IT)

Method 3: the issuing platform

If you know the signature platform, log in to your account to access the full audit trail:

• precise date and time

• signer's IP address

• OTP entered

• cryptographic fingerprint

Validity indicators

Indicator | Meaning

✅ Green "Valid Signature" | Authenticity and integrity confirmed

⚠️ Yellow "Unknown validity" | Certificate not recognised but signature correct

❌ Red "Invalid Signature" | Document modified or signature corrupted

🕐 "Qualified timestamp" | Date proven by a QTSP

If the signature is invalid

Possible causes:

• document modified after signing

• certificate expired or revoked

• service provider not recognised by the reader

• corrupted file

In this case, contact the issuing platform for clarification.

Verifying an AES signature

For an AES, the PDF contains the cryptographic signature plus a pointer to the audit trail of the platform. Verify both:

• signature in the PDF (Adobe Reader)

• audit trail on the issuer's side

Use case: verification during an audit

A statutory auditor receives 50 electronically signed contracts to audit. Procedure:

• Open each PDF in Adobe Reader → verify status

• Check consistency (date, signer)

• Request audit trail from platform for sample

• Verify SHA-256 fingerprint 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 to 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, how can I do it?

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

Does the signature remain valid if I reprint the PDF?

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

Can I verify a signature from 10 years ago?

Yes, for PAdES-LTA formats. More basic formats may have issues with obsolete 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. It 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.