It depends on the bow and the cam design. Most bows are adjustable by either changing the cam itself (mathews) or by changing a module on the cam or cams (most others). Some are adjusted with a stop on the cam. Some designs you have to have a bow press to change the modules, others you don't. My bowtech you can change the draw length and adjust let off without a bow press. My darton requires a press to change the module. Hoyts do not need a press and my girlfriends alpine micro does not need a press either.

To change a string, harness or cam you obviously need a press. There might be one or two people that could do it without one, but it would be difficult. The limbs are holding quite a bit pressure, even when not drawn. I have done it with a kids bow with a really low draw weight. I got it apart, but couldn't get it back together without a press. I couldn't imagine doing it with a 70 lb bow.

Paul