PDF Signature Verification — Free Online Digital Signature Checker

PDF Signature Verification — Free Online Digital Signature Checker. Verify the digital signatures in a PDF: checks that the signed bytes are unchanged, that each signature is cryptographically valid and whether the signer certificate was valid.

Runs in your browser — nothing is uploaded. Need to perform PDF signature verification on a contract or legal document?

Our free digital signature checker recomputes the hash of the bytes each signature covers and compares it with the digest the signer signed, then verifies the signature itself with the public key of the signer certificate.

For every signature you see whether the document is unchanged since signing or was modified afterwards, whether the signature is cryptographically valid, the signing time, and whether the signer certificate was valid at signing time and is still valid today.

Simply drop your signed PDF — nothing is uploaded. Unlike server-based PDF signature verification services, all checks run in your browser with node-forge and the WebCrypto API, so signed contracts, court filings and financial records never leave your device.

Supported: CMS/PKCS#7 signatures (adbe.pkcs7.detached, ETSI.CAdES.detached, adbe.pkcs7.sha1) and RFC 3161 document timestamps with RSA, RSA-PSS or ECDSA keys.

What it cannot do: there is no trust store in the browser, so it does not check whether the certificate chains to a trusted authority, and it does not check revocation — use Adobe Acrobat Reader or an official validation service when you need a legal verdict.

Our free PDF signature verification tool checks every digital signature embedded in a signed PDF document — directly in your browser, with nothing uploaded to any server. How to Verify a PDF Digital Signature Drop or select your signed PDF in the upload zone.

For each signature, the tool hashes the bytes listed in its /ByteRange and compares the result with the message digest the signer signed. It verifies the signer's signature over the signed attributes with the public key of the signer certificate.

It compares the certificate's validity period with the signing time and with today, and lists the certificates with their PEM data. What the Results Mean Document unchanged since signing : the signed bytes match.

Modified after signing : the signed bytes were altered. If data was appended after a signature (an incremental update, such as a second signature or a comment), the tool says so.

Signature cryptographically valid : the signature value matches the certificate's public key. The signing time comes from a timestamp token, the signed signing-time attribute or the PDF signature dictionary, and the tool shows which.

What Is Not Checked Certificate trust is not checked because there is no trust store in the browser, and revocation (CRL/OCSP) is not checked either.

A valid result therefore proves the document matches what the holder of that certificate signed, not that the certificate belongs to a trusted signer. Use Adobe Acrobat Reader or an official validation service for a legal verdict.

Supported Signature Types CMS / PKCS#7 signatures (adbe.pkcs7.detached, ETSI.CAdES.detached, adbe.pkcs7.sha1) and RFC 3161 document timestamps, with RSA, RSA-PSS and ECDSA (P-256, P-384, P-521) keys.

The legacy adbe.x509.rsa_sha1 format is reported as unsupported. Privacy & Security All processing runs client-side.

Your PDF never leaves your device, making this tool safe for contracts, legal briefs, NDAs, financial statements, and other confidential signed documents.

Related Tools After verifying you can edit PDF metadata , merge PDFs , or reorder pages — all in the same browser-based toolbox.

Frequently asked questions

How do I check the digital signature in a PDF?

Drop the signed PDF on the upload area or click to browse. Each signature gets a result card: Document unchanged since signing or Modified after signing, Signature cryptographically valid or invalid, the signing time, the certificate status at signing time and today, and the certificate list with View PEM.

What exactly is verified?

The tool hashes the bytes listed in the signature's ByteRange with the digest algorithm named in the signature and compares the result with the signed message digest. It then verifies the signer's signature over the signed attributes with the public key of the signer certificate (RSA, RSA-PSS or ECDSA).

Does a valid result mean I can trust the signer?

Not on its own. Certificate trust is not checked because there is no trust store in the browser, and revocation is not checked either. A valid result proves the document matches what the holder of that certificate signed. For a legal verdict use Adobe Acrobat Reader or an official validation service.

What does Signed version unchanged, but the file was changed after signing mean?

The bytes covered by the signature are intact, but more data was appended afterwards as an incremental update, for example another signature, a filled form field or a comment. Those later changes are not protected by that signature.

Why does it say No digital signatures found?

The PDF contains no embedded digital signature or is damaged. A drawn or typed signature image is not a cryptographic digital signature and is not detected. Signatures in an unsupported format are still listed, with a message saying why they could not be checked.

Is my signed PDF uploaded?

No. The file is read and verified in your browser with node-forge and the WebCrypto API; it is never sent to a server.

How to use this online tool

PDF Signature Verification — Free Online Digital Signature Checker is designed for fast browser workflows when you need to format, validate, convert, decode, encode, generate, or inspect data without opening a heavy desktop app. Start with the input field or visible options, review the result, then copy or download the output for the next step.

Private processing in your browser

PDF Signature Verification — Free Online Digital Signature Checker keeps the normal processing step local in your browser. That is useful for code snippets, tokens, documents, configuration values, text samples, and other material that should not be sent to a remote service unless you explicitly choose to share it.

When this tool is useful

Use PDF Signature Verification — Free Online Digital Signature Checker for repeatable developer tasks, technical documentation, QA checks, quick conversions, debugging, content cleanup, and internal team workflows. The page focuses on clear inputs, immediate feedback, and output that is easy to reuse in code, reports, tickets, emails, or notes.

Practical tips

Before copying the final result, check important details such as spacing, casing, filenames, encoding, token structure, line breaks, or output format. Small checks prevent mistakes when the result is reused in source code, API requests, documentation, spreadsheets, or shared files.