Embed, Flatten or Remove PDF Annotations in Swift for iOS

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//
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//  Copyright © 2016-2025 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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/// Shows how to embed, flatten and remove annotations with `PSPDFProcessor`.
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final class AnnotationProcessingExample: Example {
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    // MARK: Lifecycle
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    override init() {
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        super.init()
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        title = "Annotation Processing"
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        contentDescription = "Shows how to embed, flatten and remove annotations with PSPDFProcessor"
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        category = .documentProcessing
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        priority = 10
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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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        return AnnotationProcessingPDFViewController(document: document)
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    }
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}
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/// Processes annotations of it's document.
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private final class AnnotationProcessingPDFViewController: PDFViewController {
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    // MARK: Lifecycle
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    override func commonInit(with document: Document?, configuration: PDFConfiguration) {
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        super.commonInit(with: document, configuration: configuration)
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        let actions = [("Embed", #selector(embedAnnotations)), ("Flatten", #selector(flattenAnnotations)), ("Remove", #selector(removeAnnotations))]
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        let barButtonItems = actions.map { title, selector in
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            UIBarButtonItem(title: title, style: .plain, target: self, action: selector)
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        }
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        navigationItem.setRightBarButtonItems(barButtonItems.reversed(), for: .document, animated: false)
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    }
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    // MARK: Bar Button Item Actions
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    /// Presents document with annotations embedded.
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    @objc
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    private func embedAnnotations() {
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        let embeddedDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "embedded")
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        // We want to embed annotations, i.e. keep them editable.
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        guard processAnnotations(.embed, document: document!, newDocumentURL: embeddedDocumentURL) else {
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            presentErrorMessage("Embedding annotations failed.")
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            return
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        }
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        presentProcessedDocument(embeddedDocumentURL)
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    }
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    /// Presents document with annotations flattened.
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    @objc
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    private func flattenAnnotations() {
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        let flattenedDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "flattened")
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        // We want to flatten annotations, i.e. make them non-editable.
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        guard processAnnotations(.flatten, document: document!, newDocumentURL: flattenedDocumentURL) else {
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            presentErrorMessage("Flattening annotations failed.")
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            return
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        }
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        presentProcessedDocument(flattenedDocumentURL)
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    }
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    /// Presents document with annotations removed.
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    @objc
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    private func removeAnnotations() {
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        let removedAnnotationsDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "removedAnnotations")
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        // We want to remove annotations.
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        guard processAnnotations(.remove, document: document!, newDocumentURL: removedAnnotationsDocumentURL) else {
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            presentErrorMessage("Removing annotations failed.")
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            return
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        }
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        presentProcessedDocument(removedAnnotationsDocumentURL)
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    }
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    // MARK: Document Processing
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    /// Processes annotations.
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    ///
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    /// - Parameters:
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    ///     - annotationChange: Which `PSPDFAnnotationChange` to perform.
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    ///     - document: `Document` containing pages with annotations.
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    ///     - newDocumentURL: `URL` that's used as output file URL of `PSPDFProcessor`.
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    /// - Returns: `true` iff processing succeeded, `false` otherwise.
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    private func processAnnotations(_ annotationChange: AnnotationChange, document: Document, newDocumentURL: URL) -> Bool {
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        // Set up configuration to flatten the document.
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        guard let configuration = Processor.Configuration(document: document) else {
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            print("Processor configuration needs a valid document")
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            return false
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        }
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        // Process all types of annotations.
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        configuration.modifyAnnotations(ofTypes: .all, change: annotationChange)
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        // We are only interested in the pages that actually have annotations.
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        configuration.includeOnlyIndexes(pagesWithAnnotations(document))
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        do {
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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: newDocumentURL)
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        } catch {
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            print("Error while processing document: \(error)")
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            return false
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        }
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        return true
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    }
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    // MARK: Helper
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    /// Filters pages with annotations.
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    ///
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    /// - Parameter document: `Document` containing pages to filter.
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    /// - Returns: `NSIndexSet` of pages with annotations.
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    private func pagesWithAnnotations(_ document: Document) -> IndexSet {
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        let pagesWithAnnotations = NSMutableIndexSet()
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        let allTypesButLinkAndForms = Annotation.Kind.all.subtracting([.link, .widget])
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        for page in 0..<document.pageCount {
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            if document.annotationsForPage(at: page, type: allTypesButLinkAndForms).isEmpty { continue }
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            pagesWithAnnotations.add(Int(page))
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        }
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        return pagesWithAnnotations as IndexSet
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    }
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    /// Presents a processed document.
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    ///
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    /// - Parameter processedDocumentURL: `URL` of processed document.
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    private func presentProcessedDocument(_ processedDocumentURL: URL) {
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        let processedDocument = Document(url: processedDocumentURL)
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        let pdfController = PDFViewController(document: processedDocument)
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        pdfController.navigationItem.setRightBarButtonItems([], for: .document, animated: false)
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        let navigationController = UINavigationController(rootViewController: pdfController)
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        present(navigationController, animated: true, completion: nil)
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    }
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    /// Presents an error message.
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    ///
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    /// - Parameter message: Error message to present.
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    private func presentErrorMessage(_ message: String) {
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        let alert = UIAlertController(title: "Error", message: message, preferredStyle: .alert)
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        alert.addAction(UIAlertAction(title: "Dismiss", style: .default))
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        self.present(alert, animated: true, completion: nil)
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    }
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}
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extension AnnotationProcessingPDFViewController: 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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}