     /// UIBarButtonItem used to override the default action button
     fileprivate var actionButton: UIBarButtonItem?
     
+    /// Backbutton used in case of being overrridden
+    fileprivate var backButton: UIBarButtonItem?
+    
     /// Background color to apply to the collectionView.
     public var backgroundColor: UIColor? = .lightGray {
         didSet {

        collectionView.register(PDFPageCollectionViewCell.self, forCellWithReuseIdentifier: "page")
        
        navigationItem.rightBarButtonItem = actionButton
        
        let numberOfPages = CGFloat(document.pageCount)
        let cellSpacing = CGFloat(2.0)

    /// - parameter actionStyle:       sytle of the action button
    ///
    /// - returns: a `PDFViewController`
    public class func createNew(with document: PDFDocument, title: String? = nil, actionButtonImage: UIImage? = nil, actionStyle: ActionStyle = .print, backButton: UIBarButtonItem? = nil) -> PDFViewController {
        let storyboard = UIStoryboard(name: "PDFReader", bundle: Bundle(for: PDFViewController.self))
        let controller = storyboard.instantiateInitialViewController() as! PDFViewController
        controller.document = document
