try this software Inscape (link). It should be freeware solution.
How it works is shown in video below. Impotant thing is that PDF must contain objects, scanned PDF will not work at all.
Source of this knowledge is from SEU2012 from Jason Wooden (PDF attached).
Once you have 2d geometry from PDF in 2D Draft environment, use "copy / paste" or "Create 3D command to move 2D geometry to 3D sketches.