About Us

About PDF SignCheck

Free, privacy-first cryptographic verification for digitally signed PDF documents.

Our Mission

PDF SignCheck was built to solve a simple but frustrating problem: digitally signed government documents showing “Signature Not Verified” in standard PDF viewers like Adobe Acrobat.

Millions of official documents — Aadhaar cards, DigiLocker certificates, income tax returns, caste certificates, driving licenses — are digitally signed by Indian government Certifying Authorities. Yet when opened in Adobe Acrobat, they display a confusing yellow question mark because Adobe's proprietary trust list doesn't include these CAs.

We built PDF SignCheck to make cryptographic signature verification accessible, instant, and free — no installations, no manual trust configuration, no technical knowledge required.

How It Works

PDF SignCheck performs full PKCS#7/CMS cryptographic signature verification:

  • Signature Extraction: We parse the PDF structure to locate and extract PKCS#7 signature blocks embedded in the document.
  • Hash Verification: We independently compute the hash (digest) of the document's byte ranges and compare it against the signed digest to detect any tampering.
  • Certificate Chain Validation: The signer's certificate chain is validated against 80+ trusted root Certificate Authorities from the Mozilla CA trust store.
  • Verified Stamp Output: Once validated, we stamp the PDF with a visual “Signature Valid ✓” badge that renders correctly on any device, browser, or PDF reader.

For a detailed technical walkthrough, read our complete guide on verifying PDF digital signatures.

Privacy & Security

We understand that digitally signed documents often contain sensitive personal information. Our privacy commitments:

🔒 Zero Storage PolicyFiles are processed entirely in-memory. Nothing is ever written to disk, stored in a database, or retained after verification completes.
🛡️ No Data CollectionWe do not read, log, or analyse the contents of your PDF documents. Only the cryptographic signature metadata is processed for verification.
⚡ Immediate DiscardOnce the verified PDF is returned to your browser, all in-memory data is immediately garbage-collected. There is no backup, no cache, no retention period.

Read our full Privacy Policy and Terms of Service for complete details.

Technical Stack

PDF SignCheck is built with modern, well-tested open-source technologies:

  • Cryptographic Engine: Built on node-forge for PKCS#7 parsing, hash computation, and certificate chain validation.
  • PDF Processing: Uses pdf-lib for PDF incremental saving and visual stamp embedding.
  • Certificate Trust Store: Validates against the Mozilla CA trust store — an open, community-maintained list of 80+ globally trusted root CAs.
  • Application Framework: Next.js with server-side processing for secure, fast verification.

Founded By

PDF SignCheck was created by Minhaj, a developer who experienced the government document verification problem firsthand. After spending hours trying to manually trust Indian government CA certificates in Adobe Acrobat — only to realize the fix was computer-specific and didn't transfer — he built PDF SignCheck to automate the entire process.

The tool has since grown to support verification of documents from DigiLocker, UIDAI, Income Tax, e-District portals, and more. It serves users across India and internationally who need to verify and share government-issued PDFs.

Contact Us

For questions, feedback, or enterprise enquiries, reach us at: