Actually you can make use of anim notifies + decals to do this. What you need to do is fire-off an event when your character’s feet touch the ground - thats means two events( one for each foot). Within this event, you can do a trace to get the location where the touch occured and put a foot-print decal there.
Another way is to simply spawn a particle effect when the feet touches ground - again using anim notify. But it wont be as accurate as the first method.
Please read the docs on anim notifies. If I remember correctly there is a youtube video posted in Unreal engine channel which shows how to do this (the second method)
Here is the link: https://www.youtube.com/watch?v=LpgvyhVcxM4&list=PLZlv_N0_O1gaCL2XjKluO7N2Pmmw9pvhE&index=80