One of the quirks in working with XMP metadata is that the names for the various categories of information appear to change between InDesign and Acrobat. Thus if you put text in ID's "Description" it will show up in the "Subject" in Acrobat. Note that Tomaxxi offers a free panel for IDCS5-6 that can makes these categories easier to access.
As you already know, IPTC adds many more categories, and XMP's extensibility means you can add your own, or others Adobe does not include.
Ah I see, Thanks for that response and explanation. I thought I had tried description but I must have only tried keywords.
I appreciate your help, thanks again!
You could do it in Adobe Bridge, with several files at the same time, you could also select a PDF and an INDD to make changes in the metas together.