The PDF began as Camelot, a plan to tame PostScript for screens
In 1991 Adobe co-founder John Warnock wrote a paper for a project code-named Camelot. He wanted a trimmed-down PostScript, the language printers used, that would show a page exactly the same on any screen and any computer. Two years later Adobe released the result as the Portable Document Format.
PostScript was never meant for that job. It is a full programming language, with loops and branches, built to stream one-way print jobs: the printer gathers commands until told to output a page, then renders it. To draw page 50 accurately you had to run everything for pages 1 to 49 first, because any earlier command might affect it. PDF strips away the control flow while keeping the drawing commands. Converters such as Adobe Distiller effectively compile a PostScript program by unrolling loops and cutting unused branches, leaving a static description.
Everything needed to display a document travels in one file: typeset text, vector shapes, photographs, embedded fonts, compressed where useful. Later versions added forms, annotations, layers, video, 3D objects, encryption, digital signatures and file attachments.
Adobe published the specification free of charge in 1993, but early on PDF was mainly a desktop publishing tool, competing with formats like DjVu, Envoy and even Adobe's own PostScript. Adobe kept control until 1 July 2008, when PDF became the open standard ISO 32000-1 and Adobe granted royalty-free use of its relevant patents. Even so, that edition still depended on some proprietary Adobe technologies, such as its XML forms system, which many other programs never supported.
The clean break came with PDF 2.0, published by ISO in 2017 with no proprietary technology among its required references. A corrected second edition followed in December 2020, and in April 2023 the PDF Association made the standard free to download.
Source: PDF
