There's a new app that may be of interest.

No cost for data, no advertisements, no in-app purchases.

It's available for 6 trails (and counting), AT, CDT, PCT, LT, CT and JMT. Manual and tracking GPS features, add way points, SI or Standard, reverse data book trail direction, filter way points, way point alarms and tons of other cool features.

You'll love 'sim mode'. You can hike the trail in the comfort of your arm chair on a rainy winter evening.

Downloading topo maps is solid and reliable. Download a single topo section or the whole trail. Check it out (PCT shown):