Workaround for rdar://19592583 (see https://gist.github.com/steipete/8df39fea0d39680a7a6b)

PSPDFWindow.m

@interface PSPDFWindow ()
@property (nonatomic, strong) UIViewController *realRootViewController;
@end

@implementation PSPDFWindow

- (void)setHidden:(BOOL)hidden {
    [super setHidden:hidden];

    // Workaround for rdar://19592583
    // Adding a second UIWindow breaks rotation logic in iOS 8
    // If we remove the root view controller, we disallow rotation which solves the iOS 8 regression.
    if (hidden) {
        self.realRootViewController = self.rootViewController;
        [super setRootViewController:nil];
    } else {
        if (self.realRootViewController) {
            [super setRootViewController:self.realRootViewController];
            self.realRootViewController = nil;
        }
    }
}

- (void)setRootViewController:(UIViewController *)rootViewController {
    [super setRootViewController:rootViewController];
    self.realRootViewController = nil;
}

@end

this is so messed up. Thanks though Peter, You've saved me hours again.

8 years later, still helpful. Thank you!