Here's how to do it, without Adobe Illustrator:
- Make your source file (PDF / Scan etc) into bitonal TIFF image (I use Bluebeam and Irfanview in the video, but you could easily save the PDF to image using GSView)
- Open in Inkscape
- Vectorize using Path - Trace Bitmap... Brightness steps, set to 2.
Untick: Smooth, Stack scans, Smooth corners and Optimize paths.
(this step makes the black and white image into lines and outlines)
- Save as EPS
- Open in GSView (requires Ghostscript and pstoedit)
- Save as DXF (using Convert to Vector format). From here, you can get to AutoCAD or Navisworks easily...
- Open in AutoCAD
- NWCOUT and/or
- Append the DXF directly to Navisworks
- Scale and position appropriately
The file sizes at each step look like this: