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PDF Signature Checker

See who signed a PDF, whether it was changed after signing, and whether the signing certificates are trusted and still valid. Everything is checked on your device and the file never leaves it.

  • Free

    no account needed

  • On device

    runs in your browser

  • No upload

    the file stays with you

Choose a PDF to check

Click to browse or drag and drop - PDF files up to 100 MB

Signatures are checked on your device and the PDF is never uploaded

What does a PDF signature checker do?

A digitally signed PDF carries one or more cryptographic signatures inside the file. Each one locks the document bytes at the moment of signing and names the certificate of the person or organisation that signed. A signature checker reads those signatures and reports whether the document is still exactly what was signed and who stands behind it.

  • Checked in your browser

    This checker runs the whole verification in your browser. It locates every signature in the file, recomputes the digest over the signed bytes, verifies the signature value with the signer's public key, walks the certificate chain up to a public root, and checks that no certificate has expired.

  • Nothing to install

    Contracts, invoices, court filings, diplomas, and government forms are often signed this way. Checking them here takes a second and needs no Acrobat, no plugin, and no account.

What gets checked

Each signature is graded on three independent checks, and the full certificate chain is shown so you can judge the signer yourself.

  • Integrity

    The signed byte ranges are hashed again and compared with the digest the signer sealed. A single changed byte in the signed content fails this check. Changes made after signing, such as a later signature or a filled form, are reported separately.

  • Authenticity

    The signer certificate must chain, link by link, to a root in the Mozilla root store. Self-signed and private certificates verify their content but show as not trusted, and so do many national and Adobe-approved authorities that browsers do not ship.

  • Validity period

    Every certificate in the chain is checked against its own validity dates as of today. Long-term validation, trusted timestamps, and revocation lists are not consulted, so an expired certificate marks the signature as not verified even when it was valid on the signing date.

Who checks PDF signatures?

  • Legal and finance teams

    Legal and finance teams verify that a signed contract or invoice was not edited after the counterparty signed it, and that the signature really came from the certificate it claims.

  • HR and admissions

    HR and admissions staff check diplomas, certificates, and identity documents that arrive as signed PDFs before accepting them.

  • Developers and IT teams

    Developers and IT teams inspect the signature type, digest algorithm, and certificate chain of documents produced by their own signing pipelines, without installing desktop software.

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Frequently asked questions

Still have questions? Contact support.

Is my PDF uploaded anywhere?

No. The file is read and verified entirely in your browser. Nothing is sent to our servers or anyone else, and the tool keeps working with the network disconnected.

What does "Verified" mean here?

A signature is marked verified when all three checks pass: the signed content is unchanged, the certificate chain ends in a root from the Mozilla root store, and no certificate in the chain has expired. If any check fails, the signature is marked not verified and the failing check is named.

Why does a genuine signature show as not trusted?

Trust is checked against the Mozilla root store that browsers use for websites. Many document-signing authorities, including government and Adobe Approved Trust List roots, are not in it. Adobe Acrobat may show the same signature as trusted because it ships a different list. The certificate chain is displayed so you can check the issuer yourself.

Which signature types are supported?

CMS/PKCS#7 signatures, which is what Acrobat, PAdES, and nearly every signing tool produce (adbe.pkcs7.detached, ETSI.CAdES.detached, and adbe.pkcs7.sha1), with SHA-1, SHA-256, SHA-384, or SHA-512 digests. Legacy adbe.x509.rsa_sha1 signatures and document timestamps are listed but not verified.

Does it check timestamps, revocation, or long-term validation?

No. Trusted timestamps (RFC 3161), certificate revocation (OCSP and CRL), and long-term validation (LTV) data are not evaluated. Expiry is judged as of today, so a signature made with a certificate that has since expired shows as not verified even if it was valid when signed.

Can I check a password-protected or multiply signed PDF?

A PDF with several signatures shows one card per signature, in the order they were applied, and notes when a later change means an earlier signature no longer covers the whole file. Password-protected PDFs cannot be checked: remove the password with our Unlock PDF tool first.