There's quite a few films that document walking the entirety of one of the big trails in the US (think PCT or AT), but the one I've wanted to watch recently is called "Only The Essential," and documents the journey of two friends on the PCT from Mexico all the way to Canada. I won't try to sell it to you (I haven't even watched it yet!) but I will encourage you to watch the two trailers and the sneak peek below to see if it'd interest you, too. I think it'll be available on vimeo soon!
"In the summer of 2013 Casey Gannon and Colin Arisman thru-hiked the Pacific Crest Trail with cameras in hand. "Only The Essential" is the story of their 5 month, 2668 mile journey on foot from Mexico to Canada across the wilderness of California, Oregon, and Washington."
"Feel the rhythm & power of 2668 miles of footsteps on the Pacific Crest Trail."
"Enjoy the uncut last 5 minutes of Only The Essential. This segment captures the final 100 miles of a 2668 mile, 5 month wilderness journey."