PDF

PDF (Portable Document Format) is a file format created by Adobe in 1993 and standardized as ISO 32000. Its whole point is that a document looks exactly the same everywhere: same fonts, same layout, same page breaks, whether you open it on a phone, print it, or email it across the world. That reliability is why contracts, invoices, manuals, and forms still travel as PDF.

Unlike a Word file, a PDF is fixed. It describes precisely where every character, line, and image sits on the page, so nothing reflows or shifts when someone else opens it. A single PDF can hold text, vector graphics, raster images, fonts, form fields, digital signatures, and metadata all in one container.

Most of what you do with PDFs day to day is reshaping that container: joining several files into one, splitting a long report into pieces, shrinking it for email, or locking it with a password. The format is flexible enough that none of those edits break how it displays.