I just wanted to add my response quickly, I have not read thru the other responses. My first vet told me that I should not "clean-up" in front a (specifically a yorkie). She said that it shows them that they can go somewhere else.
I use the larger pads (36 x 32/36?) This seemed to solve the problem of them peeing on the edge. I've never used a litter box for them so I don't know if that has anything to do with it or not. I had 2 cats and one of them would not use the box if it had more than 1 day worth of mess in it! So I had enough of litter boxes. lol
I can leave the pad down for more than 2-3 pees whereas I used to change the smaller ones every 3rd time. Poop gets picked up right away. I will change it at night though when they go into the pen...I would want to sleep with all that smell.
They are also outdoor trained too. Good luck.