I noticed that my door skin had come unglued on the bottom. What should I use to reglue it on.

Get some Bonding material.  Evercoat makes a real good one.  It is available in quart size.  Mixes like Bondo.  Put it in a Large cyringe, Like you would use to inject spices and stuff into a Turkey or Meats in general.  Removing the oversized needle, and just using the plastic tip.  Make sure you rinse the area real well. If there is dirt it will only happen again. Roughen it somehow, if you can, so that the Bonding agent has something to adhere to.  Inject the material into the seam and clamp it across the entire area. Wiping the excess.  Let it set for several hours, before you unclamp it.  24 hours is best.  You should be good as new.  I did this a while back and it worked really well.

I have the same problem with my doors, only at the very bottom, will a epoxy work, or can they be spot welded, anybody have any experience with either