PDF refers to portable document format, which is a type of electronic document file developed by Adobe Systems. The primary purpose of PDF is to enable sharing of electronic documents in a style that resembles printed documents.
Adobe began to conceptualize PDF in 1991. It was a way to eliminate the use of paper in office settings while still being able to share large documents, magazines and newspapers over electronic communication, such as email. As of 2014, PDF is often used to share secure documents and gather signatures from people electronically, eliminating the need for printed copies traveling via postal mail. PDF files require specific software to open and view, such as Adobe Reader.