Johnbarb,
You won't need to trace the lines over an image if your .pdf is a vector .pdf.
The process I use to transform vector .pdf into .skp is by using inkscape (an excellent opensource vector graphics software).
1 - Import the pdf into inkscape
2 - Export it as dxf
3 - Import into sketchup (there are some dxf in/out plugins but I never tried them because I have pro version)
4 - Scale dxf with the measurement tool
5 - For texts there is a dxf text import plugin by Tig that is very handy.
For those plugins search Sketchucation Plugin Store,
For exporting to .svg you can use the svg plugin rich pointed or, if you have sketchup pro or a pdf printer installed in your system, you can print/export a .pdf from sketchup or layout and import it to inkscape again. You'll get a file that you can then save in .svg wich is the native inkscape format.
Hope this sheds some more light into that matter.
Best regards,
JQL