developer

I am a relatively new developer (1 published iPhone/iPad app). My question: "Is there a way to allow a co-developer to download the app while in the development stage to their device? Can they do this without having XCode installed on their device? This co-developer is a graphic designer, not a programmer, so therefore does not need to know xCode at all. They just need to be able to run the app so as to see how the graphics work in order to be able to submit new graphic designs.