The .dwg file extension stands for drawing. One of the oldest file types, it was initially conceived in the 1970s for use with the early Computer Aided Design (CAD) devices for 2D and 3D drawings. The DWG format is licensed to Autodesk for their AutoCAD application which is the de facto standard for CAD drawings. Autodesk have robustly resisted attempts to reverse engineer the DWG format by other freeware applications building watermark protection into certain versions. The DWG files created by CAD applications are used industrially by architects, engineers and designers.
A .DWG file is a binary file that contains vector image data and metadata. The vector image data provides instructions to the CAD application about how to display the DWG on screen. The metadata may contain a variety of information on the file including location specific data and also client data. Files created using AutoCAD 14 also have a file verification checksum included, which validates that the file was created using AutoCAD.
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.