Portable Document Format (PDF): The global standard for capturing and
reviewing rich information from almost any application on any computer
system and sharing it with virtually anyone, anywhere: Adobe | Wikipedia
Anyone can view a PDF file: Use the free Adobe Reader software: Adobe Reader
Almost all computer files can be converted to a PDF file. Examples include Word, PowerPoint, Excel, graphics, etc. Basically anything that can be printed from a computer can be converted into a PDF file.