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).

These standards have been recognised by the UK Government's policy paper Viewing government documents along with HTML.