override func viewDidLoad() {
    createMenu()
}

private func createMenu() {
    let highlightItem = UIMenuItem(title: "Highlight", action: #selector(highlight(_:)))
    UIMenuController.shared.menuItems = [highlightItem]
}
    
@objc private func highlight(_ sender: UIMenuController?) {
    guard let currentSelection = pdfView.currentSelection else { return }
    let selections = currentSelection.selectionsByLine()
    guard let page = selections.first?.pages.first else { return }

    selections.forEach { selection in
        let highlight = PDFAnnotation(bounds: selection.bounds(for: page), forType: .highlight, withProperties: nil)
        highlight.endLineStyle = .square
        page.addAnnotation(highlight)
    }

    pdfView.clearSelection()
}