Free Online PDF Signature Verification

Validate Signature Authenticity and Document Integrity

In the PDF electronic signature system, a signature is encrypted data embedded in the document, used to prove that the signing action occurred and can be verified. A digital certificate is an electronic credential issued by a trusted Certificate Authority (CA), binding the signer’s identity to their public key, usually conforming to the X.509 international standard. A trusted timestamp is generated by an independent Timestamp Authority (TSA) to prove that the signature existed at a specific point in time, usually following the RFC 3161 standard. If no trusted timestamp is detected, the signature time may come from the signer’s local system. Signature algorithms are used to create and verify digital signatures. This tool currently supports internationally recognized RSA algorithms and does not support SM2 or other non-standard algorithms. After verification, the system will return the corresponding results: Not Modified: The file has not been altered after signing and its content remains consistent with the signed version. Modified: The file has been changed after signing, and the original signature no longer ensures integrity. Signature Valid: The file contains a verifiable electronic or digital signature, has not been modified after signing, and the signature can be trusted. Signature Invalid: The file contains a signature, but verification failed, possibly due to tampering, expired certificates, or an untrusted certificate chain. No Signature Found: The document does not contain a signature that meets PDF signature standards, or the signature algorithm/format cannot be recognized. Note: This tool mainly supports PDF files and international electronic signature standards. It does not currently support certain Chinese electronic signature standards or formats, such as SM2, OFD (Open Fixed-layout Document), or GB/T 38540. For files signed using these standards or algorithms, it is recommended to use a dedicated verification tool compliant with Chinese national standards.