Yes, Acrobat 5 certainly was a Carbon app. I bought mine when I had gotten my first second-hand new-world Mac, a B&W G3, and setting up OS X for the first time - 10.2.0. The same bundle worked in OS 9 and 10.2. I believe the last version to run in 9 was Acrobat 5.05.

Many of the Adobe programs released just prior to CS1 were Carbon and ran fairly well on later systems also. Acrobat 5, Indesign 2, Photoshop 7, Illustrator 10, Premiere 6, After Effects 5.5. If the installer complains about a later system you might be able to just copy over the installed components from an earlier system and re-authorize the programs. They could very well run on anything from OS 8.6 to 10.5.XX.

Let's hear it for the one company who wanted to develop a 64-bit Carbon API!