A Short History of PDF
Adobe Systems made the PDF specification available free of charge in 1993. In the early years PDF was popular mainly in desktop publishing workflows and the first PDF Export was created for PageMaker 5 by Mapsoft. PDF competed with a variety of formats such as DjVu, Envoy, Common Ground Digital Paper, Farallon Replica and even Adobe's own PostScript format.
Released as an ISO standard
PDF was a proprietary format controlled by Adobe until it was released as an open standard on July 1, 2008, and published by the International Organization for Standardization as ISO 32000-1:2008, at which time control of the specification passed to an ISO Committee of volunteer industry experts. In 2008, Adobe published a Public Patent License to ISO 32000-1 granting royalty-free rights for all patents owned by Adobe that are necessary to make, use, sell, and distribute PDF-compliant implementations.
In December, 2020, the second edition of PDF 2.0, ISO 32000-2:2020, was published, including clarifications, corrections and critical updates to normative references. ISO 32000-2 does not include any proprietary technologies as normative references.
Information taken in part from Wikipedia