You can't directly place files into an application's document folder on the device as a part of the deployment. However, you can copy them from your (read only) bundle into the application's document folder.
To obtain a reference to an item in your bundle, you can use:
NSBundle *appBundle = [NSBundle mainBundle];
NSString *bundlePath = [appBundle pathForResource:@"XXXX" ofType:@"xxx"];
You can then load the data and save it as you would normally. There's more info on this process in the following question (amongst others): iphone copying folder from bundle to documents
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…