FIrst you need to learn how to USE your cad and scale, rotate, and mirror. If you rescale the drawing by .04921 you will find it is then at the scale you want.
But aren't these questions you should be asking BOBCAD
? THey should have a PDF to dxf convertor built in.
PS: I did not see the first broken chain in the drawing. NO arcs you say? You did not provide a vectored PDF. (;-)
I does have a money back guaranty
(;-)TP