Portable Document Format (PDF) is an open standard for document exchange. This file format created by Adobe Systems in 1993 is used for representing documents in a manner independent of application software, hardware, and operating systems. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other information needed to display it.
In 1991 Adobe Systems co-founder John Warnock outlined a system called "Camelot" that evolved into the Portable Document Format (PDF).
While the PDF specification was available for free since at least 2001, PDF was originally a proprietary format controlled by Adobe, and was officially released as an open standard on July 1, 2008, and published by the International Organization for Standardization as ISO 32000-1:2008. In 2008, Adobe published a Public Patent License to ISO 32000-1 granting a royalty-free rights for all patents owned by Adobe that are necessary to make, use, sell and distribute PDF compliant implementations.