I love spray adhesive (3M Photo Mount almost exclusively) for a lot of things, but it's an aerosol and gets all over EVERYTHING if you're not careful - I spray outside, in the garage, or in the house inside a mostly closed box which works surprisingly well. If you use it I'd suggest making a mask first - just cut a hole in a sheet of paper in the shape & size of where you want the confetti to go, lay it over your real paper (maybe tape them together on the back with paper tape or blue painter's tape), and cover anything else on your real paper so it doesn't get sprayed.
Alternatively, since it's paper confetti, I'd probably use a Zig pen, or a paintbrush with a liquid glue like 3M Scotch Quick Dry or The Best Glue Ever. Just paint on where you want it and add your confetti. You can also easily add more glue & confetti this way.