non è gratuito, ma si può usare 15 volte, meglio di nulla, in caso di emergenza ;)

http://www.anydwg.com/dwf-to-dwg-home.html

http://anydwg.net/download/dwfdwg.exe

-Convert DWF to DWG and DXF.

-Supports all DWF entity types exported by AutoCAD, including arcs, elliptical arcs, ellipses, true type fonts and etc.

-Supports the DWF multi-page specification.

-Restores the layers in DWF, renders entire DWF pages.

-Extracts embedded Images from the DWF file.

-Batch conversion ability allows you to convert an unlimited number of DWF files at a time.

-It is a standalone program, AutoCAD not required.