Add watermark to all PDF pages using Swift for iOS

1
//
2
//  Copyright © 2016-2025 PSPDFKit GmbH. All rights reserved.
3
//
4
//  The Nutrient sample applications are licensed with a modified BSD license.
5
//  Please see License for details. This notice may not be removed from this file.
6
//
7

8
import PSPDFKit
9
import PSPDFKitUI
10

11
/// Uses `PSPDFProcessor` to draw on all current pages of a document.
12
final class DrawOnPagesExample: Example {
13

14
    // MARK: Lifecycle
15

16
    override init() {
17
        super.init()
18

19
        title = "Draw Watermarks On Pages"
20
        contentDescription = "Uses PSPDFProcessor to draw watermarks on all current pages of a document"
21
        category = .documentProcessing
22
        priority = 14
23
    }
24

25
    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
26
        let document = AssetLoader.document(for: .welcome)
27
        guard let configuration = Processor.Configuration(document: document) else {
28
            fatalError("Processor configuration needs a valid document")
29
        }
30

31
        let renderDrawBlock: PDFRenderDrawBlock = { context, page, cropBox, _ in
32
            // Careful, this code is executed on background threads. Only use thread-safe drawing methods.
33
            let text = "PSPDF Live Watermark"
34
            let pageText = "On Page \(page + 1)"
35
            let stringDrawingContext = NSStringDrawingContext()
36
            stringDrawingContext.minimumScaleFactor = 0.1
37

38
            let textAttributes: [NSAttributedString.Key: Any] = [
39
                .font: UIFont.boldSystemFont(ofSize: 30),
40
                .foregroundColor: UIColor.red.withAlphaComponent(0.5)
41
            ]
42

43
            let pageTextAttributes: [NSAttributedString.Key: Any] = [
44
                .font: UIFont.boldSystemFont(ofSize: 20),
45
                .foregroundColor: UIColor.black.withAlphaComponent(0.5)
46
            ]
47
            // Add text in the bottom right corner
48
            context.translateBy(x: (cropBox.size.width / 2) + 30, y: cropBox.size.height - 200)
49
            text.draw(with: cropBox, options: .usesLineFragmentOrigin, attributes: textAttributes, context: stringDrawingContext)
50
            // Add second text below the first text
51
            context.translateBy(x: 0, y: 30)
52
            pageText.draw(with: cropBox, options: .usesLineFragmentOrigin, attributes: pageTextAttributes, context: stringDrawingContext)
53

54
        }
55

56
        configuration.drawOnAllCurrentPages(renderDrawBlock)
57

58
        let processedDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "processed")
59

60
        // Process annotations.
61
        // `PSPDFProcessor` doesn't modify the document, but creates an output file instead.
62
        let processor = Processor(configuration: configuration, securityOptions: nil)
63
        processor.delegate = self
64
        try! processor.write(toFileURL: processedDocumentURL)
65

66
        let processedDocument = Document(url: processedDocumentURL)
67
        return PDFViewController(document: processedDocument)
68
    }
69
}
70

71
extension DrawOnPagesExample: ProcessorDelegate {
72
    nonisolated func processor(_ processor: Processor, didProcessPage currentPage: UInt, totalPages: UInt) {
73
        print("Progress: \(currentPage + 1) of \(totalPages)")
74
    }
75
}