PDF

Portable Document Format, a fixed-layout format used to represent documents independently of the hardware, software and operating system used to create them. This was developed and is owned by Adobe Systems Inc.

PDF reader software is free, while PDF creation software must be purchased (or is an integral part of certain DTP software). Generally, only users of the full Adobe Acrobat program can modify such documents but author proofs can be created in Acrobat that include tools allowing authors to annotate the PDF with requests for changes to the proof.

PDF is one of the competing standards for e-books.

This definition is extracted (and expanded on) from the book Getting Published: A Companion for the Humanities and Social Sciences by Gerald Jackson and Marie Lenstrup. It was first referred to in the blog Getting Published in a post on what is typesetting.