Mark,
It all depends on how that PDF was created for whether or not it can be turned into cad linework. And, as a word of caution, you don't typically want to use the linework that is auto generated, simply because of how inefficient it was created/converted. Sometimes that linework is great for a base file reference that is xref'd into your design file, and sometimes it is just as quick to draw usable linework from scratch (using the image as a reference, then removing the image).

We have a pretty cool webinar that goes over the ins and outs of working with an Image, including working with PDF's and whether or not it will come in as an image or as linework.
Drawing Setup: Using An Image

Please also see the links below for other suggested workflows and use of PDF's, and let us know if you have further questions we can help you with!
Best PDF Practices
PDF Import
PDF Xrefs and CAD – Fixing Draw Order Display Issues