Don't worry about the paper. You can use a putty knife scraper to get most of it up. Your underlayment for a wood floor will smooth the surface well enough. Your pallet floor looks great...but belongs in a cabin....way to heavy for a trailer on the move. You can get the same look with a lot lighter product.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."