Signature Verification Service

Secured Signing’s Signature Verification Service lets you check whether a PKI-signed document is genuine and unaltered, free, with no account or software install required. Upload any digitally signed PDF and we’ll confirm the signer’s authenticity and whether the file has changed since it was signed.

Built on ISO 27001-certified, PKI-based technology designed for non-forgeability and non-repudiation. Secured Signing has been verifying signed documents since 2010.

Signature Verification Service

How does PKI signature verification work?

Think of it like a tamper-proof seal. When a document is digitally signed, a unique code gets locked to that exact file. If even one word changes afterward, the code no longer matches, so checking the code tells us instantly whether the document is genuine and untouched.

Here’s what happens when you verify a document:

  1. You upload the signed PDF.
  2. We create a fingerprint of the document as it is right now.
  3. We unlock the original fingerprint that was sealed into the signature when it was first signed.
  4. We compare the two fingerprints.
  5. You get your answer: if they match, the document is genuine and hasn’t been changed since signing. If they don’t match, something’s off — either the file was altered, or it wasn’t signed with the key we’re checking against.

No technical knowledge needed on your end — you just upload the file and we handle the comparison.

What type of documents can you verify?

We can verify any PDF document which has been digitally signed using PKI technology. The document can be of any length and you can use both our online service to verify the document or out offline service if you’d prefer a more secure approach or have a large number of documents to verify.

Ready to check a document with Secured Signing.

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Is signature verification free?

Yes. Anyone can use Secured Signing’s Signature Verification Service to check a PKI-signed PDF — you don’t need a Secured Signing account or subscription.

Standard e-signature platforms often confirm a signer clicked “sign,” but not that the file is cryptographically untampered. PKI verification checks the actual data against a mathematically linked signature, so it detects any change to the document, even a single character, after signing.

Yes. The service is open to anyone, whether or not the document was signed through Secured Signing, as long as it uses PKI-based digital signatures.