Swapping Lock On Exterior Door
buy a cheap set of holesaws. This one is only $8 if you use a 20% off coupon. 

https://www.harborfreight.com/1-in-2-12-in-carbon-steel-hole-saw-set-11-pc-68114.html

buy a set that has the correct diameter holesaw.  create a template by drilling the correct diameter into a scrap of 3/4" plywood. attach the plywood template to the door using clamps or screws.  go ahead and drill the new hole in the door.  

if it is the large hole on the face of the door, you can prevent splintering by drilling in two steps.  drill the new hole only halfway deep. remount the template on the other side and drill the remainder.  

if it is the small hole on the edge of the door, clamp a scraps of 2x4 to door, one to the front and one to the back, then mount the  plywood template by screwing it into the 2x4 scraps.