Technical articles on PDF digital signature verification, browser-side cryptography, PAdES compliance, and building privacy-first document workflows.
Adobe's warning bar reports the worst verdict among every signature in the document. What produces it, and how to get the failing check instead.
Adobe's red X reports byte coverage, not tampering — a signed PDF is designed to grow. The four causes behind the one message, and how to tell them apart.
Adobe's yellow warning means the document is intact but the certificate does not chain to a trusted root — not that the signature is invalid.
PDF.js renders signed PDFs but never cryptographically verifies them. The difference between drawing a signature appearance and checking it.
Verify digitally signed PDFs entirely client-side with JavaScript and WebAssembly. The document is never uploaded — the cryptography runs in the browser.
Web viewers show the grey placeholder a signing tool baked in. How VerifyKit draws the real verdict on the signature field, inside the PDF canvas.
Run PDF signature verification headlessly in Node.js, Deno or Bun — batch processing, CI/CD pipelines and server-side validation workflows.
PAdES conformance levels under ETSI EN 319 142, and how VerifyKit detects B-B, B-T, B-LT and B-LTA for eIDAS compliance.
Contracts, medical records, legal documents — why WebAssembly verification in the browser keeps them private and never uploads them anywhere.