What is a PDF file?
PDF (Portable Document Format) was created by Adobe in 1993 so a document would look exactly the same on any computer and any printer. It became an open ISO standard, ISO 32000, in 2008, and anyone can now make or read PDFs without paying Adobe.
A PDF stores each page as a fixed layout: text with its fonts, vector drawings and embedded images, each placed at an exact position. That is why it is the default for forms, invoices, contracts, CVs and printed material. The same strength makes PDFs awkward to edit. Text may be split into fragments, and a scanned PDF holds only pictures of pages, with no text to select until you run OCR.
PDF at a glance
| Full name | Portable Document Format |
|---|---|
| File extensions | |
| Created by | Adobe; an open ISO standard (ISO 32000) since 2008 |
| Introduced | 1993 |
| Compression | Mixed: text and vectors stay sharp; photos inside are usually JPG |
| Transparency | Pages can contain transparent objects |
| Animation | No |
| Opens on | Every computer and phone; browsers have built-in viewers |
| Best for | Documents that must look the same everywhere: forms, invoices, CVs |
How to open a PDF file
Every browser opens PDFs: drag the file into a tab. To change one, start with the right tool: Edit PDF to add text, PDF to Word to rewrite it, or Compress PDF when it is too large to email.