I've owned a G4 sawtooth long time ago, and as far as I know, Tiger (10.4) is the last OS you can install.
(at the top of the page: Maximum OS: 10.4.11)
So it seems that upgrading the OS is not even an option.
Maybe buying a second hand printer that works on Tiger is an affordable option?
Thanks. I guess that when I want to print something, I shall have to put the file on a flash drive and use that on my laptop, which has no problem with my current printer (OS 5 minimum) or the one I plan to get. I had only hoped to use the older printer with the very old G4 Sawtooth, which still works just fine but isn't used much. Looks like it may be time to retire it – or at least, as soon as I don't need it for very old files. I backed it up, so I don't worry about losing anything.
Thanks, Niel. As you can see from my reply, below, I'll just have to use workarounds (printing from another printer) until I finally get rid of the Sawtooth. Too bad, because I'm not even sure that it would be of use to a nonprofit. I don't think there still are printers and other peripherals being made that will work with anything older than Tiger (OS 10.5).
It's good (though disappointing) to have an end to my search. Still hoping that I may still find a way to adapt my HP Deskjet 1000 (J11a) so it will work with the Sawtooth. It is supposed to work only with OS 10.5, but some people have indicated that it may be possible to install a driver that would work. Very doubtful, I'm afraid, and he search for a "cure" could be extremely time consuming.
Thanks again to both of you who responded to my query.