Free ZWCAD Viewer for CAD DWG File Viewing and Plotting. ZWCAD Viewer runs on different operating systems such as Windows (32-bit & 64-bit), Mac OS and Linux. With ZWCAD Viewer, drawings can be viewed in all kinds of frequently used file formats like dwg, dwf, dwfx, dxf and dwt. ZWCAD Viewer is able to measure distance between objects, area of a closed shape, mass and volume of a 3D model, regions or coordinates on the drawings.