         collectionView.register(PDFPageCollectionViewCell.self, forCellWithReuseIdentifier: "page")
         
         navigationItem.rightBarButtonItem = actionButton
+        if let backItem = backButton {
+            navigationItem.leftBarButtonItem = backItem
+        }
         
         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) -> PDFViewController {
        let storyboard = UIStoryboard(name: "PDFReader", bundle: Bundle(for: PDFViewController.self))
        let controller = storyboard.instantiateInitialViewController() as! PDFViewController
        controller.document = document

        } else {
            controller.title = document.fileName
        }
        
        controller.backButton = backButton
        
        if let actionButtonImage = actionButtonImage {
            controller.actionButton = UIBarButtonItem(image: actionButtonImage, style: .plain, target: controller, action: #selector(actionButtonPressed))
