PDF Format version history
The PDF standard is developped by the American company Adobe Systems. PDF is also an standardized, open format, listed under the ISO reference 32000-1:2008 (PDF 1.7).
A new version of the PDF standard, called "PDF 2.0", is actually being developped (ISO/NP 32000-2 - Document management-Portable document format-Part 2: PDF 2.0).
(Work in progress..)
For more information about PDF version history, please check Wikipedia:Portable_Document_Format