The .mpp file extension is the default file type created by Microsoft Project. Microsoft Project is part of the Microsoft Office product set. A .mpp file will typically contain a list of tasks that make up a particular project and allow the critical path of a project to be defined. These will contain tasks, owners, inter-dependencies, timescales. Microsoft Project also allows for visual aids such as a gannt chart to be created within the file.
The .mpp is a propriety file type created by Microsoft. Older .mpp files created by Microsoft Project before 1998 can only be opened by Microsoft Project 1998. The portability of an .mpp to other applications or platforms is restricted, with only a few options available.
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.