This is an odd one. It's a Chooser device that allows you to print to screen and see your document reduced to fit in the window or full size when you zoom in. That's not odd though, but very useful. What's odd is that I believe there is a freeware version of Preview (perhaps an earlier version) that has almost the same functionality, and even stranger is that the exact same Chooser device comes with Full Impact 2.0. Sounds like someone's doing well with the non-exclusive licenses. I can't say too much about Print Previewer because it is so transparent. You simply switch to Print Previewer in the Chooser (or use the included FKEY to switch and then switch back to whatever you were printing to before) and then print normally. You get a graphical representation of your document in reduced form and you can zoom in by clicking on an area. A second click zooms back out.
Print Previewer isn't usually as good as the Preview feature built into programs like FileMaker Pro and Nisus, but it certainly beats wasting paper for the rest of the programs. It's a good thing Nisus has its own Preview mode, though, since it doesn't seem to like the Print Previewer Chooser device, and keeps telling me that I have to do a Page Setup, which I've done several times since I selected Print Previewer. So it's not perfect. Minor incompatibilities aside, I highly recommend Print Previewer because it can save paper when you're printing from a program like WriteNow, which has no Preview function.