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 only reliable and accurate conversion to be made are vector images, which are typically higher quality than bitmap files. And this is something that vector drawing programs like Adobe Illustrator and Inkscape won't do. What else can I use as a 3D file to use as a vector image converter? It's possible to convert a 3D CAD file to another format, using a program such as Vector Works. But you've still got the problem of how do you know whether the bitmap is an accurate representation of the CAD file. This makes your bitmap an approximation of the line, not an accurate 3D representation. So, unless you're using a CAD program that handles it accurately, or a 3D object creator like Blender, it's unlikely that the 3D file itself is that useful. The other issue is that you may have to do a lot of conversion in order to get.