The so-called reminder of signature conflict when updating the same software is because every Android software needs a signature to use. For apex launcher, if you don't need pro version, go to google play market to download it, where it is genuine. Updating and upgrading through google play will not prompt for signature conflict. If you need a pro version, it must be a cracked version. Since it is a cracked version, it must have been modified by someone else. Different people modify it, and their signatures are different.