如何在ios应用程序中显示和编辑现有PDF文件

import PDFKit

let pdfView = PDFView()
view.addSubview(pdfView)

if let pdfURL = Bundle.main.url(forResource: "example", withExtension: "pdf") {
    if let pdfDocument = PDFDocument(url: pdfURL) {
        pdfView.document = pdfDocument
    }
}

let annotation = PDFAnnotation(bounds: CGRect(x: 100, y: 100, width: 200, height: 50), forType: .text, withProperties: nil)
annotation.contents = "This is a text annotation"
pdfView.document?.page(at: 0)?.addAnnotation(annotation)

pdfView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
    pdfView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
    pdfView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
    pdfView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
    pdfView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
])