How this stuff actually works

Every tool page tells you the steps. These guides go one level deeper, into why PDFs behave the way they do, so you can make a better call than just guessing at settings.

• Why your PDF is so big, and what actually shrinks it

  Images, embedded fonts, and scan resolution are almost always the real cause of a bloated PDF. A walkthrough of where the bytes go and which fix matches which cause.

• PDF passwords, protection, and redaction: what each one actually does

  These three sound similar and protect against completely different things. What each one guarantees, what it doesn't, and how to combine them for a document that's genuinely safe to share.

More guides get added as the tool set grows. If there's a PDF or image question you keep running into, tell us — it might become the next one.