If you want true, water slide decals, they’ve gotten expensive. However, if you have an ink jet printer, there are kits. (Basically a special paper and 1or 2 spray cans.) it’s important to know that the kit decals (to my knowledge, which is not recent) are fairly translucent, so they will barely read on a dark surface. Or, say on a bright red, something like yellow would read as an orange.
I‘m sure another member will chime in with more current info on the kits.
The other technology that I’ve used, “rub downs” (also called INTs, or dry transfers) are also expensive—with good art, a single color sheet, letter sized, is around $100—so really not priced for non-professional use. (Although you could fit a lot of pedals worth of words on that sheet… and they can be made in pretty much any color, including foils, etc. but multi color gets more expensive fast.) I have 8 pedals I’m using, ready to be painted and then graphics, but I’m waiting until my old business (I’m now retired) needs to order some for a job, so I can fit these into the order.