Design Review works with a variety of file formats, including: DWF, DWFx, DWG, and DXF (requires installation of free DWG TrueView software); Adobe PDF; as well as image file types such as BMP, JPG, GIF, PCX ,PCT, PNG and more. It is a freeware DWF viewing application that's efficient.
Here are some screenshots to illustrate the features and user interface of this application: