Without more info on what kind of printer, etc, the best I can offer is that he try to open the document with AppleWorks (which should have been included with his iMac) and print it from there.
The newest AppleWorks can open Word docs, so that may be the easiest solution (again, without more info on what kind of printer he has).
Basically, he'll need to find an OS 9 installer for his printer, run it in Classic, and hope to heck it works. Sometimes it does, sometimes it doesn't.
Or he could upgrade to Office v.X.
