Add watermark to all PDF pages using Swift for iOS

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//
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//  Copyright © 2016-2026 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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/// Uses `PSPDFProcessor` to draw on all current pages of a document.
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final class DrawOnPagesExample: Example {
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    // MARK: Lifecycle
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    override init() {
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        super.init()
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        title = "Draw Watermarks On Pages"
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        contentDescription = "Uses PSPDFProcessor to draw watermarks on all current pages of a document"
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        category = .documentProcessing
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        priority = 14
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.document(for: .welcome)
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        guard let configuration = Processor.Configuration(document: document) else {
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            fatalError("Processor configuration needs a valid document")
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        }
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        let renderDrawBlock: PDFRenderDrawBlock = { context, page, cropBox, _ in
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            // Careful, this code is executed on background threads. Only use thread-safe drawing methods.
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            let text = "PSPDF Live Watermark"
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            let pageText = "On Page \(page + 1)"
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            let stringDrawingContext = NSStringDrawingContext()
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            stringDrawingContext.minimumScaleFactor = 0.1
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            let textAttributes: [NSAttributedString.Key: Any] = [
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                .font: UIFont.boldSystemFont(ofSize: 30),
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                .foregroundColor: UIColor.red.withAlphaComponent(0.5)
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            ]
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            let pageTextAttributes: [NSAttributedString.Key: Any] = [
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                .font: UIFont.boldSystemFont(ofSize: 20),
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                .foregroundColor: UIColor.black.withAlphaComponent(0.5)
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            ]
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            // Add text in the bottom right corner
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            context.translateBy(x: (cropBox.size.width / 2) + 30, y: cropBox.size.height - 200)
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            text.draw(with: cropBox, options: .usesLineFragmentOrigin, attributes: textAttributes, context: stringDrawingContext)
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            // Add second text below the first text
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            context.translateBy(x: 0, y: 30)
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            pageText.draw(with: cropBox, options: .usesLineFragmentOrigin, attributes: pageTextAttributes, context: stringDrawingContext)
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        }
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        configuration.drawOnAllCurrentPages(renderDrawBlock)
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        let processedDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "processed")
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        // Process annotations.
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        // `PSPDFProcessor` doesn't modify the document, but creates an output file instead.
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        let processor = Processor(configuration: configuration, securityOptions: nil)
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        processor.delegate = self
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        try! processor.write(toFileURL: processedDocumentURL)
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        let processedDocument = Document(url: processedDocumentURL)
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        return PDFViewController(document: processedDocument)
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    }
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}
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extension DrawOnPagesExample: ProcessorDelegate {
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    nonisolated func processor(_ processor: Processor, didProcessPage currentPage: UInt, totalPages: UInt) {
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        print("Progress: \(currentPage + 1) of \(totalPages)")
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    }
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}