# Custom Graphics Demonstrates adding a watermark to a PDF page. ## Overview You can add a custom drawing to a page or annotation by overriding that class’s draw method. Adding drawings to pages can be useful for adding custom layered effects or, as shown in this sample, watermarking a document. ### Register the Delegate and Set the Page Class The [`ViewController`](doc://com.apple.documentation/documentation/UIKit/UIViewController) class first initializes a [`PDFDocument`](/documentation/PDFKit/PDFDocument) instance and sets its delegate to `self`. ```swift // 1. Set delegate document.delegate = self pdfView?.document = document ``` The delegate, of type [`PDFDocumentDelegate`](/documentation/PDFKit/PDFDocumentDelegate), implements a [`classForPage()`](/documentation/PDFKit/PDFDocumentDelegate/classForPage()) method. This method returns [`AnyClass`](doc://com.apple.documentation/documentation/Swift/AnyClass) and declares that all instances of [`PDFPage`](/documentation/PDFKit/PDFPage) for the document presented through [`PDFView`](/documentation/PDFKit/PDFView) should instantiate the subclass `WatermarkPage`. This subclass, found in `WatermarkPage.swift`, implements custom drawing. ```swift // 2. Return your custom PDFPage class /// - Tag: ClassForPage func classForPage() -> AnyClass { return WatermarkPage.self } ``` `ViewController` loads a URL to the `Sample.pdf` file through the app’s main bundle. This URL is then used to instantiate a `PDFDocument`. On success, the document is assigned to the `PDFView`, which was set up in Interface Builder. The delegate is assigned before the document, so `classForPage()`, a `PDFDocumentDelegate` method, is implemented. This method returns the `PDFPage` subclass used for custom drawing. ### Override the Draw Method `WatermarkPage` subclasses `PDFPage` so that it can override the [`draw(with:to:)`](/documentation/PDFKit/PDFPage/draw(with:to:)) method. This method is called by `PDFDocument` to draw the page in a `PDFView`. All custom drawing for a PDF page should be done through this mechanism. ```swift // 3. Override PDFPage custom draw /// - Tag: OverrideDraw override func draw(with box: PDFDisplayBox, to context: CGContext) { // Draw original content super.draw(with: box, to: context) // Draw rotated overlay string UIGraphicsPushContext(context) context.saveGState() let pageBounds = self.bounds(for: box) context.translateBy(x: 0.0, y: pageBounds.size.height) context.scaleBy(x: 1.0, y: -1.0) context.rotate(by: CGFloat.pi / 4.0) let string: NSString = "U s e r 3 1 4 1 5 9" let attributes: [NSAttributedString.Key: Any] = [ NSAttributedString.Key.foregroundColor: #colorLiteral(red: 0.4980392157, green: 0.4980392157, blue: 0.4980392157, alpha: 0.5), NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 64) ] string.draw(at: CGPoint(x: 250, y: 40), withAttributes: attributes) context.restoreGState() UIGraphicsPopContext() } ``` Custom drawing methods should always be thread-safe and call the superclass method, which is required to draw the original `PDFPage` content. Custom drawing code can execute before or after this superclass call, although order matters. If your graphics run before the superclass call, they’re drawn below the `PDFPage` content. Conversely, if your graphics run after the superclass call, they’re drawn above the `PDFPage` content. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)