Zoom to specific PDF annotations easily

class CustomPDFViewController: PDFViewController {
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        // Find the first annotation for demonstration purposes.
        guard let document = self.document, let annotation = document.annotationsForPage(at: 0, type: .all).first else {
            return
        }

        self.documentViewController?.zoom(toPDFRect: annotation.boundingBox, forPageAt: 0, animated: true)
    }
}

@interface CustomPDFViewController : PSPDFViewController
@end

@implementation CustomPDFViewController

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    // Find the first annotation for demonstration purposes.
    PSPDFAnnotation *annotation = [[self.document annotationsForPageAtIndex:0 type:PSPDFAnnotationTypeAll] firstObject];

    if (!annotation) {
        return;
    }

    [self.documentViewController zoomToPDFRect:annotation.boundingBox forPageAtIndex:0 animated:YES];
}

@end