The PDF is everywhere — contracts, bank statements, ebooks, tax forms. But beneath its calm, predictable surface sits a format with some genuinely odd capabilities. Here are seven things you probably did not know about PDF.

  1. PDFs can contain 3D models. A PDF can embed interactive 3D objects you can rotate and zoom — engineers use this to ship CAD models inside a single document.
  2. They can run JavaScript. Forms can include scripts for calculations and validation. Useful — and also a reason to be careful with files from unknown sources.
  3. Text is often selectable, not flat. A real PDF stores text as vectors, so you can search, copy and read it with screen readers — unlike a scanned image.
  4. They can have layers. Like a design file, a PDF can hold optional layers that show or hide content depending on the viewer.
  5. Fonts can travel with the file. A PDF can embed its fonts so it looks identical on every machine, even one that does not have them installed.
  6. Bookmarks are a real feature. That little sidebar table of contents is stored as structured navigation — not just visual decoration.
  7. The format was once proprietary. PDF was a commercial Adobe format before it became an open ISO standard in 2008.
The PDF is less a single file than a small, self-contained application for displaying a document.

Once you know what is inside, the format starts to make a lot more sense — including why a well-made PDF looks perfect on any device.