OK. I'm still using Photoshop 7, though it served most of my needs just fine. This thread prompted me do some poking around and had some good results. You can set up the free OpenOffice Draw program to import vectored PDFs and edit them-- sometimes. There are plenty of exceptions, but it's worth a try. You have to install an OpenOffice addon called the "PDF Import Extension" (download file, then go to Tools > Extension Manager).
Using OO Draw I quickly changed the color of a Hummer model from red to yellow without interfering with the overlaying details. Some PDFs require a password to edit, even if you can view/print without a password. One didn't even open and locked up the program, too. Still, It's one way to do the job. I blame (bleeping) Adobe for tinkering with the PDF format so much over the years to sell software updates.
Wade