Hi, I use a 20" G4 iMac and 12" G4 PowerBook both running Tiger's last update that you mention, 10.4.11, and running Office 2004 for Mac's Word, as well as Excel and PowerPoint. I don't think there is a specific Mac-version of "Office 2003" as you mention, I don't ever remember seeing one, that's sounds like a PC version year update, often not in sync with a Mac release. I highly recommend Office 2004 with Tiger 10.4.11.
• Office has always been an 800-lb gorilla, bloated with feature gak many users never need, although it does serve power-users pretty well.
• I used Office 98 back in the OS 9 days and really loved it.
• Then Microsoft really screwed the pooch with Office v.X, back around 2001 or so when OS X came out, a real mess, and remapped many keyboard command combinations (without including a user-(re)mapping feature, but solved it with 2004) in order to "unify" similar functions between programs, which drove me crazy in Excel because my fingers had been doing many many specific combinations since v1.5 in 1988 and I still can't adjust. The customizable toolbar has helped with a lot of deep menu commands to eliminate keyboard commands.
• I have not upgraded to the current Office 2008, simply because I don't need more bloatware, nor can I justify spending the $$$, nor do I need the new features. Also remember that Office 2008 came out in the Intel + Leopard era and in many ways addresses issues there which don't exist under Tiger.
• If you really only need Word primarily, consider looking for a Student/Teacher Edition of Office 2004 on eBay or something. Perhaps even just Word from that version, if they sold it alone, I can't recall.
Good luck!