🚀 go-pugleaf

You say your initial response to this "Is there a way..." question was no. My initial response to such questions is always yes--the real question is do you have the tools and are you willing to do the work. We are dealing with computers, and they can be programmed to do almost anything.

In this case, you basically need to compare two index documents and add modified versions of any unique entries from the CHM index to the PDF index. Since I primarily use the Mac version of Framemaker, I would use AppleScript to do this, and it would be a fairly easy task. On a PC, I'd suggest FrameScript, but I am not familiar enough with its capabilities to be sure it is up to the task. Otherwise, you could export both to MIF and write some sort of filter script/program to compare them and add the desired entries to the PDF index.

Another route would be to compare the index markers in the source documents and add modified versions of any unique markers in the CHM to the source for the PDF. But the required tools and techniques would be pretty much the same.