The DWF file is a “digital plot” file. Similar to a digitize/vectorize/scan of a paper drawing, you can also convert/recover DWF files back to DWG (using third party utilities) – but in both cases you may lose substantial amounts of information, structure and precision of the original drawing.
Both DWF/DWFx and PDF were meant to be used as reference (read-only, unchangeable) drawings – you can under-lay them directly in your model.
Conversion to the editable DWG format is not an intended operation with DWF files. DWF is a vector format containing only “low-intelligence” (plotting) entities so it cannot be fully recovered (changed) back to a standard DWG drawing.
There are a number of third-party conversion software packages on the market or you can attach the file to an Autocad drawing and print a PDF to under-lay the information into 12d Model. Refer to “2d PDF” on this process.
No specific conversion software package is recommended by 12d Model Software.
Google “DWF” for more information.