The file type .prc is an eBook format created by a French eBook company called Mobipocket which created a free software application for multiple devices including PDAs, smartphones and tablet devices. The .prc extension is actually identical to .mobi extension but is used specifically for Palm devices which only support .prc or .pdb extensions.
Amazon Kindle Apple iBooks Mobipocket Reader Desktop
PDF is a file format developed by Adobe Systems for representing documents in a manner that is separate from the original operating system, application or hardware from where it was originally created. A PDF file can be any length, contain any number of fonts and images and is designed to enable the creation and transfer of printer-ready output.
Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images and 2D vector graphics that compose the document. They do not encode information that is specific to the application software, hardware, or operating system used to create or view the document.