Dear Rich Grise:
You can save it as postscript if you have Acrobat (not Reader). Perhaps there is some way to convert this back into vector graphics.
As long as you are clear to "those who asked" that it is "just a guess"...
Assuming you have Acrobat, format the document for the largest print format you have available. Save it as a JPEG. Import the JPEG into your CAD program. Scale the image until you get the same length for different stated dimensions that they printed. "Measure" away.
Assuming you have Acrobat Reader, zoom the drawing until it fills the screen, at least the parts you care about. Hit [Prt Scr]. Open your CAD program, and insert the graphic from the clipboard. Scale as described above.
I strongly urge you to contact the supplier of your PDF with your guesses. They may warn you about bad ones...
David A. Smith