I've seen some sonar processing software that can export PDFs that have layers that you can toggle on and off. Even PowerPoint now has it. I know the push is towards "cloud" based interactions, but many clients still prefer PDF charts. This would be an incredible increase in usability of these products; to be able to turn off overlying layers, toggle labels. I think this is a very approachable goal. A more complex variation of this idea would to have layers, such as labels, or more detailed resolution surfaces (as Mosaic Datasets already do) that change as you zoom in to the PDF. If this already exists in ArcPro, let me know! If not and you think it's possible, let me know as well! Heck, let me know if you don't even think it's a good idea...