The acronym "PDF" stands for "Portable Document Format." PDF is a file type invented by Adobe Systems and initially released in 1993. As of 2014, this format for electronic document exchange is maintained by the International Organization for Standardization.
PDF files allow users to convert different document types, such as Web pages, pictures and forms, into a simple, standard format that looks like a printed page and that can be read using open source software on most operating systems. Unlike printed pages, PDF files can also include electronic enhancements like clickable links and form fields. The most common PDF reader is Adobe Reader, but there are many other free PDF readers available, including Sumatra PDF for Windows and Preview for Mac.