Geneo is right. Downloading maps is not supported however, if you truly want to "share" a "custom" map and you're really die-hard dedicated, you can. You can still create maps via creative and host them (meaning you have to exist in the world and let others join you). That's about it. There's no MCEdit or any other way to create custom maps other than vanilla creative.
Custom maps are prohibited by the Microsoft ToS and therefore by Minecraft Forum rules. If/when Microsoft changes this, I'm quite sure the forum will as well; the map sections for PC and Pocket Edition are highly popular.
The Search feature sometimes gives incomplete results. Okay, who am I trying to buffalo, it's broken (and really driving the moderators crazy).This is one of the things that went a little wonky with the forum software transition. This will get fixed, but nobody has a timetable at this point.
Since the question has been answered in several previous posts, and this thread is likely to start attracting things that would make me have to hand out warnings, I'm locking it.