LibreCAD is a free and open-source 2D CAD application that lets you edit DWG files. Using it, you can edit DWG as well as DXF files in it. You can even design a new drawing from scratch using it.

and both DWG and DXF file output options are available. Although the free trial is fairly comprehensive, you don't have an option for batch conversions. Those who need a long-term PDF to AutoCAD ...