The Portable Document Format (commonly known as “PDF”) is a file format developed in the early 1990s as a way to share computer documents, including text formatting and inline images.
From 1993 until 2007 the PDF specification (known at that time as the “PDF Reference”) was published in eight editions (1.0 to 1.7) by Adobe Systems. To promote widespread adoption from the outset, Adobe made these documents freely available and their use royalty-free.
In 2008 ISO published Adobe's PDF Reference 1.7 (with minor, non-technical changes) as ISO 32000-1. Under a special one-time agreement between Adobe and ISO, an “Adobe version” of ISO 32000-1 was made available as a free download from Adobe’s website. The PDF Association maintains links to all versions of PDF past and present.
In December 2020, ISO published the 2nd edition of PDF 2.0, ISO 32000-2:2020, the current PDF specification.