If you want to do some vector post processing on Layout Files bringing PDF into Adobe Illustrator is a great option. You can turn things on or off, change line style, added or change text.
You can also turn around and save the Illustrator files back as dwg file. CS3 and CS4 support importing and exporting to scale, so you can bring your exported dwg back to full scale.
Illustrator can also be used to bring PDF's into SketchUp as vector files using same technique. PDF opened, saved as dwg, and then imported into SketchUp.