PDF Signature Checker
What is a PDF Signature Checker?
Verify digital signatures embedded in signed PDF documents locally in your browser. Confirms document authenticity, signer certificate details, and detects whether content was altered after signing.
Why Use This Tool?
- Legal Document Verification: Verify digital signatures on signed contracts, legal agreements, and official invoices.
- Tamper Detection: Ensure PDF document contents have not been modified or corrupted since signing.
- Signer Certificate Inspection: Inspect signer identity, signing timestamp, and certificate authority info.
How to Use
- Upload a signed `.pdf` document.
- The checker parses embedded PKCS#7 / CMS signatures.
- View Signature Validation Status, Signer Name, Signing Time, and Tamper Status.
Real Working Example
Input:
Uploaded File: contract_signed.pdf
Output Result:
Signature Status: VALID (Authentic) Signer: John Doe (john@example.com) Signing Time: August 18, 2026 14:30:00 UTC Document Integrity: Content Unaltered (Byte Range Check Passed)
Important Technical Details & Security Standards
- PDF PKCS#7 / CMS Parser: Uses WebAssembly PDF-Lib and ASN.1 parsers to extract embedded digital signature byte ranges.
- Byte Range Verification: Validates digest hashes against original document byte boundaries.
- 100% Local Privacy: Sensitive PDF files are parsed locally in browser memory without server uploads.
Related Security & Crypto Tools
- PDF Text Extractor: Extract text from PDF pages.
- X.509 Certificate Decoder: Decode SSL certificates.
- Hash Text: Compute SHA256 message digests.
Frequently Asked Questions
Are my uploaded confidential PDF documents sent to a server?
No, all PDF signature parsing and cryptographic verification happens 100% locally in your web browser.
What does a valid PDF digital signature prove?
A valid signature proves the identity of the signer and guarantees that the PDF content has not been altered since signing.
Is it free?
Yes, 100% free.
What causes a PDF signature to show as invalid?
Modifying text/images after signing, corrupted byte ranges, or untrusted certificate authorities can invalidate a signature.
Does it support DocuSign and Adobe Acrobat signed PDFs?
Yes, standard PKCS#7 and CMS signatures created by Adobe Acrobat, DocuSign, or digital IDs are supported.
Is there a PDF file size limit?
There is no server limit—processing speed depends on your local computer memory.