You can save paper by printing multiple PowerPoint slides to a single sheet of paper. The trick is to rely on a printer option rather than on PowerPoint itself.
Cam Howey, one of our Canadian members, recently reminded me that it’s easy to print multiple slides on a single piece of paper. The default is one slide per one sheet of paper, but as Cam reminded me, doing so isn’t economical or efficient, and it certainly isn’t green. Instead, unless you have a specific reason for doing otherwise, print multiple slides on a single sheet of paper as follows:

Be quick to cancel the print task if the first page doesn’t suit your needs. You might need to experiment a bit before you get just the right mix. As you can imagine, the more slides you print to one sheet, the smaller the images will be. You can use these multiple slide pages to document or review a presentation, and you’ll save paper.
All of the Office applications offer this printing capability. Knowing it exists is the key — and that the printer, not Office, determines where you’ll find the option.