As you can see in some of the pleats in the two pics above, the pleat edge _does_ lie parallel to the pattern edge (e.g., the blue/black, and yellow/blue pleats in the first kilt and the triple white in the second kilt). What to do with a particular pleat depends on whether you have something that can be centered (a stripe or a color boundary), how much taper there is in the pleat (so that you don't lose elements toward the top of the pleat), how many little stripes you have to cope with, etc.