Add stamp annotation to PDF page.

ImageAnnotation.swift

class PDFImageAnnotation: PDFAnnotation {

    var image: UIImage?

    convenience init(_ image: UIImage?, bounds: CGRect, properties: [AnyHashable : Any]?) {
        self.init(bounds: bounds, forType: PDFAnnotationSubtype.stamp, withProperties: properties)
        self.image = image
    }

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

        guard let cgImage = image?.cgImage else { return }
        context.draw(cgImage, in: bounds)
    }
}

// add annotation
let image = UIImage(named: "myLogo")
let imageAnnotation = PDFImageAnnotation(image, bounds: CGRect(x: 200, y: 200, width: 200, height: 200), properties: nil)
page.addAnnotation(imageAnnotation) // Note make sure this in memory page object is not shared among multiple document