There is no adjustment on caravan doors, at least not the older ones. Unfortunately both the body and doors of caravans move over the years so become un-aligned and usually proving dificult to close. [I know we had one]
Sellotape in place over the inner part of the door where the gaps are, Leave it at the alluminium strip around the door.
Apply vaselene to the doors sealing/draft strip and the edge of the door between the sealing strip and inner frame and about 4" above the gap/s. Close the door from the inside where the gaps are squirt foam in them.
After it's set you should be able to open the door as long as you greased the sealing strip and door edge properly. Trim the foam with a sharp knife like a craft knife. You can then paint it with blackboard paint so it doesn't stand out.
bob
bob, August 2005