Editing Info.plist

I’m writing an iPad app and I want to include File Sharing to/from my Mac. The apple docs say I just have to:

Can anyone advise how I do this? Can I tell Unity to put this key in there, or must I add it by hand every time I compile?

you must put it in in xcode / in the file itself.

but keep in mind: its os 3.2+ only so for iphone iPhone OS4 only.

So I need to redo it on every compile?

Yes, my game is iPad-only, so it’s not a big deal.