PDF is the format for documents that must look the same everywhere. Adobe created it in 1993, and since 2008 it has been an open international standard, ISO 32000. A PDF stores each page as a fixed layout, with its fonts, images and graphics placed exactly, so it prints and displays identically on any device, with or without the software that made it.
How a PDF works
A PDF is a collection of objects: pages, fonts, images and the instructions that draw text and shapes in precise positions. Fonts are usually embedded in the file, so text looks right even on computers that don’t have those fonts. Because the layout is fixed rather than flowing, a PDF behaves like a sheet of paper rather than a word-processor document.
Text PDFs and scanned PDFs
PDFs come in two kinds that look identical on screen:
- Text-based PDFs come from software: Word, Google Docs, browsers, accounting tools. The letters are real text, so you can search, select and copy them, and they stay sharp at any zoom.
- Image-based PDFs come from scanners and phone scanning apps. Each page is a photograph of paper. You can’t search or copy the words unless text recognition (OCR) has been added.
This difference decides what you can do with a PDF. Extracting text, for example, only works with text-based PDFs.
What PDF is good at
- Reliable sharing. Forms, contracts, CVs, invoices and manuals arrive looking exactly as intended.
- Printing. Page sizes, margins and fonts are fixed, so what you see is what prints.
- Combining content. Text, photos and vector graphics in one file.
- Long-term archiving. The PDF/A variant is designed to stay readable for decades.
Where PDF falls short
- Editing. PDFs aren’t meant to be rewritten. Small changes are possible with editors, but substantial edits are easier in the original document.
- Reflowing. Fixed pages don’t adapt to small phone screens the way web pages do.
- File size. Scanned PDFs store every page as an image and can get large quickly.
Working with PDF pages
Many everyday PDF jobs don’t change the content at all; they rearrange pages. Merging, splitting, rotating and removing pages copy pages as they are, so nothing is lost. Converting pages to JPG or PNG turns them into pictures, and building a PDF from photos turns pictures into pages.