I have been struggling with this issue for the last few days and after all this juggling I have figured out that all I need is the current Index from the datasource method to up
To get the current index you'll have to do the following:
-(void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
NSUInteger index = [self.viewControllers indexOfObject: [pageViewController.viewControllers lastObject]];
NSLog(@"INDEX: %lu",(unsigned long)index);
}