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.
The best example that I can think of is the old GIS files created by the late 'X' computer company (which, incidentally, were based on the 'Windows' operating system). This is an example which demonstrates the complexity this can create: The original PDF file was a GIS file, and was written in the 'X' CAD software. It was then scanned, and a PDF file created. However, when scanned, the 'X' software decided it was not a GIS file. Because the scanner couldn't use the 'normal' bitmap tracing algorithm, it instead created a 'blob' of lines, which was then imported into a vector image format (which is how the vector program saw it) to be used by the bitmap tracing software tool. When the bitmap tracing algorithm saw this object as a line rather than a vector object, it was unable to accurately trace the image. The result was.