PDF

What is a PDF file? The complete beginner’s guide — what PDF means, why it beats Word for sharing, how to open PDFs, and what you can do with them.

How to password protect a PDF — the two-password model explained, 4 methods compared, and honest security grading (40-bit RC4 vs. AES-256).

How to sign PDF on phone — the zero-install iPhone method, Android options, and the honest truth about what a phone-drawn signature legally is.

How to compare two PDF files and find differences — three methods by use case, what text-extraction compare misses, and privacy warnings for contracts.

What is PDF/A format? A plain-English guide to the PDF archiving standard — what it forbids, version differences, when to convert, and honest conversion warnings.

How to fill PDF form files online — first check if your PDF is actually fillable, then the right method for interactive vs. flat forms, plus signing.

How to add watermark to PDF files — text vs. image watermarks, opacity and placement rules, page-range control, and the honest truth about what watermarks can’t do.

Learn how to split PDF into pages — one file per page, page ranges, or every N pages — with free online, desktop, and Mac methods plus honest privacy guidance.

How to add page numbers to PDF files free — including Bates numbering vs. regular page numbers, custom formats, and starting from a specific page.

What is PDF metadata? A field-by-field guide to PDF document properties — Title, Author, Keywords — plus privacy risks and how to remove metadata before sharing.