There are a lot of options for converting PDF to DXF. Many are online, meaning you upload a file to some site and ask them to return you a DXF. Creepy! Or you can download a (probably malware infested) app. I tried one of them, and it seemed to work okay. Oddly, for the PDF of the DXF drawing that I was trying to convert, it produced both an image and a DXF, and the DXF was a mess and was too big for my viewer until I saved it as a very early version of DXF, then reloaded it and selected all the lines and set the pen to .002". The result then looked basically identical to the original drawing!
The app that I used is this one. It had a 30-conversion free trial. It's normally $180.
http://www.aidecad.com/pdf-to-dxf-converter.html
This one looked nice, although it seemed a little bloated. It has
monthly licensing which is insane, but supposedly had a 14 day trial with no features disabled.
http://www.scan2cad.com/pricing/
