I'm a little late to this game, but I think I can shed light on this (at least from the perspective of how I want to use layered PDFs). I design and make PDF bag patterns and have recently purchased a few clothing patterns that have layers. It's great because, normally clothing patterns are infamous for being hard to find your cutting line. If it's a kid's pattern, say, then each size (2T, 3T, 4T, 5, etc.) will have a different colored and often line/dash pattern. But they overlap in places (since grading sewing patterns is NOT just a matter of scaling them!). Where they overlap or come close (or even if some lines print up in a similar color), it's REALLY hard to see your cutting line. So when I got these layered ones where you can just untick the boxes for the sizes you don't want and JUST print the sizes of the pattern pieces you want, I was thrilled! They then have the "MUST PRINT" layers that are all of the text, instructions, photos, etc. So that's how I want to do some aspects of my PDF bag patterns too and I often draw my shapes right in Designer! :)
