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What do you need to do to a door before hanging it to ensure that it is draughtproof, water resistant? Do you need to treat the door with wood preserve? If so, what is the best to use? How long does it take to dry?
Use a sealer on all six sides. The rest of the info is on the can.
Based on your questions, you may want to hire a door specialist.
Doors are a tricky animal and you can mess one up without too much effort. Once you've cut too much off the door, it's really hard to put it back. Power Planes, routers, circular saws, chisels, hole saws, Forstner bits are some of the tools that are used to install a door.
If you still want to hang the door, go to it but be careful.
You don't indicate if this is a pre-hung(already mounted in its own frame) door. If it is, then the exterior models usually come with all the weather stripping in place. What would be needed is a generous application of caulk along the base plate, where the bottom of the door lintel would rest and fiber insulation between the door frame and jacks after the door is installed, before installing the interior trim. Also, you might want to insure that the bottom of the exterior frame is properly flashed before installation.