Guides
How PDFs actually work
Plain explanations of common PDF problems, written by the folks building the tools that fix them.
Most PDF trouble comes from one thing: the format was designed to describe a printed page, not to store a document you can work with. It records where each glyph sits and what colour each shape is, but not which words form a sentence, which lines form a paragraph, or that a black rectangle was meant to conceal what is under it.
That gap explains an enormous amount of otherwise baffling behaviour: why a two-page file is eight megabytes, why a filled-in form shows up blank on someone else's screen, why pasted text arrives with its columns interleaved, and why redactions keep failing. These guides explain the mechanism in each case, so the fix makes sense rather than being a sequence of steps to follow on faith.
- Why is my PDF so large? What takes up the space in an oversized PDF, and which of it you can shrink without losing quality.
- Bates numbering, explained Where the convention comes from, how the format works, and the practical rules for stamping a production.
- An iLovePDF alternative that never uploads your file The architectural difference between upload-based PDF tools and in-browser ones, a tool-for-tool map, and an honest list of what we don't cover.
- How to verify an online PDF tool is private A two-minute network-tab check that separates "we care about privacy" marketing from tools that provably never upload your file.
- Why your filled-in PDF form shows up blank The annotation-layer quirk that makes form data disappear in other viewers, and how flattening fixes it for good.
- Redaction that actually works A black box over a name hides nothing: the text is still in the file and copies straight out. What real redaction does instead, and how to check a document before it leaves your hands.
- How to email a PDF that's too big Attachment limits are lower than advertised and files grow in transit. What the real ceiling is, how to get under it without wrecking the document, and what to do when it won't shrink.
- Three different things called a PDF signature An image of your signature, an e-signature service, and a cryptographic signature share a name and little else. What each one actually proves, and which you need.
- Is your PDF a scan? How to tell, and what it changes Real text and photographs of text look identical in a viewer and behave nothing alike in every tool. Three ten-second checks, and what the answer means for extraction, compression, editing and OCR.
- What's actually inside a PDF Drawing instructions, embedded fonts, image objects, hidden layers and a file format that keeps its history. A tour of the container, and why it explains the format's most confusing behaviour.
- Why text copied out of a PDF comes out wrong Jumbled columns, missing spaces, ligatures turning into boxes, pages that yield nothing at all. Why extraction fails in these specific ways, and what fixes each one.