Cadmium is a free, multi-purpose CAD software with DWG support. It can create simple or complex drawings, and supports standards used in a variety of disciplines, mechanical engineering, building design, architecture, landscape design, and more.
The combination of ribbon tools, command line and property grid helps you work faster and it is familiar and easy to use. Even if it's been years since you've spent much time on CAD, you'll be able to get up to speed, and be productive, quickly and easily.
Cadmium natively opens and saves DXF, DWG (AutoCAD) and SKP (Sketchup) files. It can also export to PDF and various image file formats.
You can create multiple viewports in the layout as well as multiple layouts in a drawing. Each layout can contain different plot settings and paper size.
The 3D toolset includes all 3D primitives as well as the basic 3D boolean operations, with which you can create complex 3D geometry.