A dwf is treated as a raster image in AutoCad. It is pretty much just an underlay image. It is a read-only reference file like a pdf. It can be converted, by various 3rd party programs but the results are often poorer than a pdf conversion.
Is it possible for you to get the original dwg file or even a dxf file of the drawing?
There are programs that will convert them for you. I've had some good luck with AutoDWG. It's not too expensive. That would always be my last resort though, if you really can't get a hold of the real files.