PDF

Portable Document Format (PDF) is a widely used format for sharing rendered print documents containing text, vector graphics and rasterized graphics and is widely seen as a descendant of Postscript.

Standardisation

Specific profiles of PDF have been standardised through ISO:

• ISO 19005-1:2005 - Document management -- Electronic document file format for long-term preservation -- Part 1: Use of PDF 1.4 (PDF/A-1)
• ISO 19005-2:2011 - Document management -- Electronic document file format for long-term preservation -- Part 2: Use of ISO 32000-1 (PDF/A-2)

Reading the ISO documents will cost you 158 CHF each (around $175 in 2014-07) (see pay-to-read standards).

The ISO standardised PDF variants have been recognised by the UK Government's policy paper Viewing government documents as an appropriate format "for static versions of documents produced for download and archiving that are not intended for editing".