What is a PDF?

PDF stands for Portable Document Format. It's a file type designed to show a document exactly the same way on every screen and printer, no matter what software, operating system, or fonts the reader happens to have.

Adobe created the format in the early 1990s to solve a frustrating problem: a document that looked perfect on one computer would fall apart on another — fonts substituted, images shifted, page breaks in the wrong place. A PDF freezes the layout so that what you send is exactly what the other person sees.

Why PDFs look the same everywhere

A PDF isn't a live document that re-flows like a web page or a word processor file. Instead, it describes precisely where every character, line, and image sits on the page, in fixed coordinates. It can also embed its own fonts, so the reader doesn't need them installed. That combination — fixed positioning plus embedded resources — is what makes a PDF so reliable for sharing.

What can a PDF contain?

• Text with exact positioning and embedded fonts
• Vector graphics (lines and shapes that stay crisp at any zoom)
• Raster images like photos and scans
• Interactive elements — form fields, buttons, and links
• Metadata, bookmarks, digital signatures, and even attachments

Is a PDF an image?

Not usually. People often assume a PDF is "just a picture of a page," but most PDFs contain real, selectable text. The exception is a scanned PDF, which really is an image of paper — there's no text data inside until you run OCR to recognise it.

Editing PDFs

Because the format was built for final documents, editing one is trickier than editing a Word file — but it's very doable. See how to edit a PDF for the practical methods, and how PDF files actually work if you're curious about the internals.