My first question is why aren't you editing the original files instead
of saved .pdfs? Are they someone else's original drawings perhaps, or
is your CAD software out of date?
Out of curiosity I tried the Illustrator idea, to find out whether this
editing method was possible. Illustrator does open the files, and they
do come in vector-based and editable, however the resulting exported
.dxf and .dwg files gave me mixed results (Use File, Export... not
File, Save As...BTW for saving .dwg and .dxf files from Illustrator).
I tried opening both .dwg/.dxf files saved from Illustrator in
SolidWorks 2006 first, and then in AutoCAD 2004. SolidWorks actually
opened the .dwg when AutoCAD wouldn't, however both files came in
exactly the same, with dimensions upside down and the whole drawing
rather scrambled. AutoCAD had errors with the .dwg file, and wouldn't
even open it, but the .dxf looks pretty darn good actually, and even
has editable text. This would still be a terribly tedeious way to do
drawing editing on a large scale, but might work in a pinch if you're
So much for .pdfs being read-only as many people believe! I suppose
there are very few (if any) digital files which are immune from
manipulation with the right tools.