Some people use bells. Put them on the front door or near the area and teach him to ring the bell to go out. You might leave the pad there in the area he is used to it and then slowly move it towards the door. Eventually he should just go to the door area.
I live in an apartment and I just take them out every couple of hours. My door is not easily visible from the house but Alphy has started going and sitting in an area near the door in hopes I notice him
.
Murphy was pad trained but my folks have come for an extended visit along with their dog which has started a territorial pp war all over my house and he's forgotten how the pads work....
Alphy is a night pooper. He won't poo in the house at all until sometime during the middle of the night he'll go either on the bathroom rug or in the laundry/kitchen rug.