Can I change an out swing door to an in swing door?

It depends. If it's a modern door, with a threshold (probably aluminum) attached to the jambs (vertical side pieces), the easiest thing might be to remove the trim from both inside and outside, cut nails or remove screws holding the jambs to the framing, remove the door with it's frame and turn it around. But then the hinges will be on the opposite side (left or right) of the opening. If that's ok, you may be able to replace the same trim on both sides, and if the door is subject to rain, you might add a little metal hood at the bottom of the exterior of the door. Also, you have to make sure there's vertical room for the door now to swing and be free of the interior floor. That's the simple way, with a lot of "ifs". And even then, you should get the help of a carpenter to make sure the door is hung plumb and level and secure and that the gaps all around are consistent and allow for swing and shrinking and swelling. If any of those conditions can't be met, you're in for a lot of adapting work to use the same door rather than buy a new one, and it should be done by someone with good experience, and they might need to use a different threshold for waterproofing and weatherstripping or they might prefer to buy a new door and hang it on the inside of the old frame, or even a new door and frame, with the old trim reapplied. I'm a remodeler and builder with 30 plus yrs experience and am used to retrofitting things in houses old and modern, and doors are pretty tricky. Exterior doors, which I'm assuming yours is, have the added challenge of waterproofing and weatherproofing, and are very sensitive to proper installation. Good luck! Steve