I have been messing with the app PDFMaps on my iPhone. Very impressive and useful. Basically, you download topos from the app’s store, then you can place pins, track your movement in real time, save routes (That’s all I have done so far). Although I also use a Garmin for backcountry mapping and navigation, this could not be more convenient and will take the place in many instances.
So far, my favorite map is from friends of the Linville Gorge. There are no good commercial maps of the wilderness area. To get the free map, 1. download the app, 2. hit the + by the search bar, 3. manually type in http://lgmaps.org/maps/lgnet/LGW20160310.pdf
My other favorite maps are for the Grandfather Ranger District since that is where I spend most of my time. Similar to a USGS topo, but much bigger (covering multiple quadrants), more data, and better marking. I also use some of the USGS typos, as well.
I believe there are a couple other similar apps but this is the only one I have tried.