A door grinding on the floor can be both annoying to live with and also damaging to the floor that it grinds against. Fortunately it is very easy to repair.
Remove hinges and bring the door outside
Doors can do serious damage if left to grind on the floor
You don't need a saw guide but they are very helpful, consider buying or making one
Tape the bottom of the door and mark off how much you want to cut off
Clamp your saw guide and trim off the excess door
Marvel at the work you just did
Put the door back on the hinges, and enjoy the free swinging door