| Extension | .pdf |
|---|---|
| MIME type | application/pdf |
| Signature | 25 50 44 46 2D (%PDF-) |
| Developer | Adobe |
| Introduced | 1993 |
| Standard | ISO 32000 |
| Type | document |
Portable Document Format
PDF is a format for electronic documents that look the same on every device: fonts, images and layout are stored inside the file. Adobe introduced it in 1993; since 2008 it has been standardised as ISO 32000.
Structure
A file starts with the header %PDF- and a version number. It is followed by objects (pages, fonts,
images), a cross-reference table pointing to them and the trailer %%EOF. Thanks to the cross-reference
table a viewer can open any page without reading the whole file.
Variants
- PDF/A - for long-term archiving: all fonts are embedded, external references are not allowed.
- PDF/X - for print production, with strict colour requirements.
- PDF/UA - accessible documents tagged for screen readers.
How to open
Any modern web browser, as well as dedicated PDF viewers and editors.