.pdf — Portable Document Format
Document application/pdf
What a .pdf file is
A fixed-layout document format that renders identically everywhere. It can embed fonts, vector graphics, raster images, form fields and digital signatures.
How to open it
Any browser, plus Preview, Acrobat and hundreds of other readers.
Worth knowing
A PDF may contain selectable text or just a scanned image. If you cannot select the text, it needs OCR before it becomes searchable.