Look at the excludedActivityTypes property of UIActivityViewController.
NSArray *items = ... // your activity items
UIActivityViewController *activityView = [[UIActivityViewController alloc] initWithActivityItems:items applicationActivities:nil];
activityView.excludedActivityTypes = @[ UIActivityTypeAssignToContact, UIActivityTypePrint ];
activityView.completionHandler = ... // your completion block
// display activity view here
