VectorWorks has this built-in to the program. However, I'm not sure if it's as good as a dedicated converter. It also depends how the PDF file originated. If it was created from the CAD application, it should have the vector data embedded in it, to allow conversion fairly easily and accurately. However if it was scanned, or created as a bitmap image, it's a bit harder. You'll need to use a bitmap tracing application. The free, open source multi-platform application Inkscape has a really good bitmap tracing algorithm, but there are other professional tools that can do it for you. This is harder and less accurate, and the resulting files won't necessarily be 'clean' CAD files. By this I mean that the lines may be made up of lots of little line segments, resulting in a large file that is much harder to use.
So, unless you have a very precise CAD/CAM/3D scanner, and an existing file set you'd like to copy as a 2D vector, check to see if there's a free/open source application that does the conversion. However, even then, you'll need to use a program designed mainly for vector files, like Inkscape. It'll be much easier to trace a 2D vector than a complex 3D model. There are also apps for tracing line segments. The two most popular are VectorTutors and Adobe Scribe. And if you want the whole file, a vector tracing program usually comes with the file, so there's an in-built converter, and you get the whole file in one go. The only trouble is that you have to be pretty precise with the line endings. If you really need to make an exact copy, then an expensive vector trace is a requirement. Vector works has this built-in.