The PDF file format started being used in earnest when [Adobe](https://en.wikipedia.org/wiki/Adobe_Inc.) made it available for free in 1993. It is the successor to PostScript but still fundamentally different, and it started being used in print production workflows around 1996. Together with the PDF file format, Adobe introduced the Adobe Acrobat software. Even today, Adobe Acrobat is Adobe's PDF viewing, manipulation, and editing solution, while Adobe Reader is the free PDF file viewer.
The first PDF file format was version 1.0. Adobe released new file format versions up to and including PDF 1.7. Typically, each new PDF version came with a new version of the Adobe Acrobat software. PDF version 1.7 was taken over by the International Organization for Standardisation (ISO) and published as ISO 32.000. From that point, ISO was the “owner” of the PDF file format and was in charge of developing new versions. While ISO standards are typically not freely available (they have to be purchased from ISO), the PDF file format is freely available through an initiative of the PDF Association.
The PDF file format is fully standardized; as mentioned above, it is now known as ISO 32.000 and is maintained by ISO. A wide range of standards use PDF as their base format. They are:
All of these are ISO standards that are created and maintained by ISO.
Starting in 2002, the Ghent Workgroup (GWG) also started standardization efforts, focusing on making targeted specifications for different market segments in graphic arts and different printing technologies. All Ghent Workgroup specifications are based on PDF/X but add more targeted requirements than the base PDF/X requirements. For that reason, the GWG specifications are sometimes referred to as PDF/X-Plus specifications.
The Ghent Workgroup recorded a webinar about PDF and PDF/X back in 2019. While it’s aging, it’s still interesting.