The .lit file type was developed and released by Microsoft in 2000. As with a number of Microsoft file formats, the main drawbacks of the format centred around its lack of compatibility with other devices. The format was wound down in 2011 with sales ceasing and the format was dropped in August 2012.
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.