I have purchased the Graco Devon pack-n-play and wondered if it can be lowered?

My son is now at the point where he can reach the frame of the pack-n-play and almost pull himself up - one day he'll topple right over if given the chance. Are those pack-n-plays meant to be lowered to the bottom so that he can actually stand in the pack-n-play without me being scared that he could get out? So I just lower the mattress pad that is on it now? Thanks.