Typically the conversion is Vector. I guess I can only speak for the AutoCad conversion...but it's vector. There is no setting that allows you to choose one or the other. Zoom in on your PDF progressively - 100%, 200%, 800% and you will either notice the blur or you won't.
I think providing your drawing consists only of wireframe images the pdf will be created in vector format. If however you have shaded images on the drawing the shaded sections will become raster.
The .pdf files that Workgoup PDM generates seem to be raster images, with lots of pixelation as I zoom in. The ones that I generate from Save As seem to be vector images, with lines and arcs and no pixelation.