PDF Reference

Free PDF header validator online. Check that a file starts with the correct %PDF- magic bytes, detect the PDF version, identify renamed non-PDF files, and view a hex dump of the first bytes - no upload required.

Free PDF MIME type checker online. Verify a file's actual MIME type is application/pdf by reading its magic bytes - detects renamed files, disguised PDFs, and non-PDFs with .pdf extensions. No upload, no signup.

Complete PDF paper size reference table. ISO A, B, C series, ANSI, JIS, and North American sizes with exact dimensions in mm, cm, inches, and PDF points. Filter, search, and download as CSV. Free online.

Free PDF password strength checker online. Instantly check PDF password strength, entropy, estimated crack time, and pass/fail against 8 security criteria. 100% private - runs in your browser, password never sent to any server.

Free PDF size calculator online. Estimate final PDF file size based on page count, image count, DPI, color mode, and compression settings. Instant results - no file upload, no signup required.

Free PDF specification reference online. Quick reference for PDF 1.0-2.0 operators, dictionary keywords, content stream commands, and features. Search, filter by version and category - no signup required.

Free interactive PDF vs DOCX comparison guide. Compare PDF and Word format across 20 features - portability, editing, security, accessibility, printing, and more. Find out which format to use for your use case.