3-D drawing files from 2-D DXF

I have a number of mechanical drawings of PCBs in 2-D generated from a PCB design system. I need height information added for some of the objects in the drawing file to realize 3-D which can then be output as SOlidWorks STEP files. Summary of requirement - take in 2-D file in .DXF format, add some height data, generate 3-D STEP file.