iOS PDFKit: make Text Widget PDFAnnotation readonly

Question

I would like to make the Text Widget PDFAnnotation readonly. I tried to set the isReadOnly flag to true, but it doesn't seem to make any difference. The user is still able to edit the annotation after tapping it.

Answer 1

I have been working on this problem for a while now and I finally found something that works. The solution for me was to use a .widget over .freeText. This method keeps the text from being selected and modified after export. I should point out that PDFs are not infallible, decompilation is possible with any PDF but for the every day office worker this is a perfect solution.

 //Don't use this - This is what most tutorials show
 //Which can be easily changed after export
 let annotation = PDFAnnotation(bounds: CGRect(x: 10 , y: 720 , width: 100, height: 50), forType: .freeText, withProperties: nil)

Use this - Swift 5

func addText(x: Int, y: Int, width: Int, height: Int, text: String, fontSize: CGFloat, centerText: Bool){
    
    //I'm using a PDFView but, if you are not displaying the PDF in the app then just use
    //let fileURL = Bundle.main.url(forResource: "MyPDF", withExtension: "pdf")!
    //let pdfDocument = PDFDocument(url: fileURL)
    //guard let document = pdfDocument else { return }

    guard let document = pdfView.document else { return }
    //I'm only using one page for my PDF but this is easy to change
    let lastPage = document.page(at: document.pageCount - 1)
    let annotation = PDFAnnotation(bounds: CGRect(x: x , y: y, width: width, height: height), forType: .widget, withProperties: nil)

    //Don't use contents and caption
    //annotation.contents = text
    //annotation.caption = text

    //Use this instead
    annotation.widgetFieldType = .text
    annotation.widgetStringValue = text

    //Check if the text should be centered
    if (centerText){ annotation.alignment = .center }

    //I'm using a custom font 
    annotation.font = UIFont(name: "calibri", size: fontSize)
    //You can use this instead
    //annotation.font = UIFont.systemFont(ofSize: fontSize)

    //Set the color
    annotation.fontColor = .black
    annotation.color = .clear
    annotation.backgroundColor = .clear

    //This is useless 
    annotation.isReadOnly = true

    //Add the annotation to the last page
    lastPage?.addAnnotation(annotation)
    
}

Answer 2

It seems to be a bug/oversight that PDFKit doesn't honor the isReadOnly attribute on annotations. However I was able to work around this by adding a blank annotation over other annotations in the document. I added a makeReadOnly() extension to PDF document that does this for all annotations to make the whole document read only. Here's the code:

// A blank annotation that does nothing except serve to block user input
class BlockInputAnnotation: PDFAnnotation {

    init(forBounds bounds: CGRect, withProperties properties: [AnyHashable : Any]?) {
        super.init(bounds: bounds, forType: PDFAnnotationSubtype.stamp,  withProperties: properties)
        self.fieldName = "blockInput"
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func draw(with box: PDFDisplayBox, in context: CGContext)   {
    }
}


extension PDFDocument {
    func makeReadOnly() {
        for pageNumber in 0..<self.pageCount {
            guard let page = self.page(at: pageNumber) else {
                continue
            }
            for annotation in page.annotations {
                annotation.isReadOnly = true // This _should_ be enough, but PDFKit doesn't recognize the isReadOnly attribute
                // So we add a blank annotation on top of the annotation, and it will capture touch/mouse events
                let blockAnnotation = BlockInputAnnotation(forBounds: annotation.bounds, withProperties: nil)
                blockAnnotation.isReadOnly = true
                page.addAnnotation(blockAnnotation)
            }
        }

    }
}