Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other form of 306 pdf needed to display it. PDF was developed in the early 1990s as a way to share computer documents, including text formatting and inline images. In those early years before the rise of the World Wide Web and HTML documents, PDF was popular mainly in desktop publishing workflows. Adobe Systems made the PDF specification available free of charge in 1993.
PDF was a proprietary format controlled by Adobe, until it was officially 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.
These proprietary technologies are not standardized and their specification is published only on Adobe’s website. Many of them are also not supported by popular third-party implementations of PDF.
On July 28, 2017, ISO 32000-2 was published by the ISO. ISO 32000-2 does not include any proprietary technologies as normative references.
A structured storage system to bundle these elements and any associated content into a single file, with data compression where appropriate. It can handle graphics and standard features of programming languages such as if and loop commands. Any files, graphics, or fonts to which the document refers also are collected. Then, everything is compressed to a single file.
A PDF file is a 7-bit ASCII file, except for certain elements that may have binary content. Comments may contain 8-bit characters. Indirect objects are numbered with an object number and a generation number and defined between the obj and endobj keywords.
An index table, also called the cross-reference table and marked with the xref keyword, follows the main body and gives the byte offset of each indirect object from the start of the file. Beginning with PDF version 1.