If your door is rubbing at the bottom, it could be due to an uneven floor, so check to see if the floor is level. If it is, then you can adjust the doorstop or weatherstripping to help cushion and protect the door, suggests Raf Michalowski from Meble Furniture.
'On the other hand, you can try installing a threshold which will help
provide cushion and support for the bottom of the door. You can also check
to see if the door is warped or sagging. If so, then you may need to
replace it with a new one.'