Writing about PDFs

Nobody independent writes about this format. The documentation belongs to Adobe, the standards belong to a committee, and everything else is written by someone selling a remediation contract. So we write it down.

Reference

How PDFs actually behave, written by people who read the spec so you do not have to.

• PDF/A, and which conformance level you actually need

  PDF/A has three parts and several conformance levels, and the differences matter for whether a file will still open in twenty years. A plain guide.

  21 September 2026

• Why your PDF is 40MB, and what actually shrinks it

  PDF file size is almost always images, and almost never the thing people try first. What each compression setting really does, and what it costs you.

  21 September 2026

• What a PDF knows about you

  PDFs carry author names, software fingerprints, timestamps and file paths in places that surviving an export or a flatten is not obvious. Where to look, and what actually removes it.

  21 September 2026

• What PDF password protection actually protects

  PDF encryption has two passwords that do very different jobs, and one of them is not really security at all. What each one stops, and what it does not.

  21 September 2026

• PDF/UA, and what tagging a PDF actually involves

  PDF/UA is the accessibility standard for PDFs. Most files that claim to meet it do not, because the part that matters cannot be added by a checkbox.

  21 September 2026

• Why your PDF fonts did not embed

  A PDF that looks right on your machine and wrong on someone else's is nearly always a font embedding problem. The causes, in the order they actually occur.

  21 September 2026

How to

The practical jobs, every way we could find to do them, compared honestly.

• How to password protect a PDF — 8 ways, and what each one actually protects

  Every practical way to put a password on a PDF, on Mac, Windows, iPhone, Android and the command line — with the encryption strength each one uses, and the two cases where a password on the file is the wrong tool.

  22 September 2026

• How to send documents securely through email — 7 methods, ranked by what they actually protect

  Email was not built to be private, and most advice about it protects the wrong thing. What each method really defends against — Gmail confidential mode, Outlook encryption, S/MIME, encrypted files, secure links — and which one to use for a passport, a payslip or a contract.

  22 September 2026

• How to send a PDF in an Instagram DM

  The Instagram app has no attach-file button, but there are five ways to get a PDF to someone on Instagram. Which one to use depends on whether you are on a phone, and whether you need to know they read it.

  22 September 2026

Roundups

Documents worth studying, gathered monthly.

• The best annual report designs of 2025, opened and inspected

  Four annual reports worth studying for their design — and what opening the actual PDF files reveals that a screenshot of the cover never will.

  21 September 2026