PDF, which stands for Portable Document Format, is a "file format created by Adobe Systems, in 1993, for document exchange." It permits creation of documents that can be read on any system with an Adobe Reader. One must have the Reader installed to view PDF documents (see Links & references below).

Formatting and fonts are set in a PDF document, so that they do not change on different systems, and preserve the font displayed in the original.

"Invented by Adobe Systems and perfected over 15 years, Adobe Portable Document Format (PDF) lets you capture and view robust information—from any application, on any computer system—and share it with anyone around the world. Individuals, businesses, and government agencies everywhere trust and rely on Adobe® PDF to communicate their ideas and vision." (Adobe)

Links & references