Pdfkit

PDFKit

Display, navigate, search, annotate, and manipulate PDF documents with PDFView, PDFDocument, PDFPage, PDFAnnotation, and PDFSelection.

Contents

• Setup
• Displaying PDFs
• Loading Documents
• Page Navigation
• Text Search and Selection
• Annotations
• Thumbnails
• SwiftUI Integration
• Common Mistakes
• Review Checklist
• References

Setup

PDFKit requires no entitlements or Info.plist entries.

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import PDFKit

Displaying PDFs

PDFView renders PDF content and handles zoom, scrolling, text selection, and page navigation.

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import PDFKit
import UIKit

class PDFViewController: UIViewController {
    let pdfView = PDFView()

    override func viewDidLoad() {
        super.viewDidLoad()
        pdfView.frame = view.bounds
        pdfView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(pdfView)

        pdfView.autoScales = true
        pdfView.displayMode = .singlePageContinuous
        pdfView.displayDirection = .vertical

        if let url = Bundle.main.url(forResource: "sample", withExtension: "pdf") {
            pdfView.document = PDFDocument(url: url)
        }
    }
}

Display Modes

Scaling and Appearance

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pdfView.autoScales = true
pdfView.minScaleFactor = pdfView.scaleFactorForSizeToFit
pdfView.maxScaleFactor = 4.0

pdfView.displaysPageBreaks = true
pdfView.pageShadowsEnabled = true
pdfView.interpolationQuality = .high

Loading Documents

PDFDocument loads from a URL, Data, or can be created empty.

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let fileDoc = PDFDocument(url: fileURL)
let dataDoc = PDFDocument(data: pdfData)
let emptyDoc = PDFDocument()

Password-Protected PDFs

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guard let document = PDFDocument(url: url) else { return }
if document.isLocked {
    if !document.unlock(withPassword: userPassword) {
        // Show password prompt
    }
}

Saving and Page Manipulation

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document.write(to: outputURL)
document.write(to: outputURL, withOptions: [
    .ownerPasswordOption: "ownerPass", .userPasswordOption: "userPass"
])
let data = document.dataRepresentation()

// Pages are zero-based. Validate indices; out-of-range calls raise exceptions.
let count = document.pageCount
document.insert(PDFPage(), at: count)
if document.pageCount > 2 {
    document.removePage(at: 2)
}
if document.pageCount > 3 {
    document.exchangePage(at: 0, withPageAt: 3)
}

Page Navigation

PDFView provides built-in navigation with history tracking.

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// Go to a specific page
let pageIndex = 5
if let document = pdfView.document,
   pageIndex >= 0,
   pageIndex < document.pageCount,
   let page = document.page(at: pageIndex) {
    pdfView.go(to: page)
}

// Sequential navigation
pdfView.goToNextPage(nil)
pdfView.goToPreviousPage(nil)
pdfView.goToFirstPage(nil)
pdfView.goToLastPage(nil)

// Check navigation state
if pdfView.canGoToNextPage { /* ... */ }

// History navigation
if pdfView.canGoBack { pdfView.goBack(nil) }

// Go to a specific point on the current page
if let page = pdfView.currentPage {
    let destination = PDFDestination(page: page, at: CGPoint(x: 0, y: 500))
    pdfView.go(to: destination)
}

Observing Page Changes

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NotificationCenter.default.addObserver(
    self, selector: #selector(pageChanged),
    name: .PDFViewPageChanged, object: pdfView
)

@objc func pageChanged(_ notification: Notification) {
    guard let page = pdfView.currentPage,
          let doc = pdfView.document else { return }
    let index = doc.index(for: page)
    pageLabel.text = "Page \(index + 1) of \(doc.pageCount)"
}

Text Search and Selection

Synchronous Search

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let results: [PDFSelection] = document.findString(
    "search term", withOptions: [.caseInsensitive]
)

Asynchronous Search

Use PDFDocumentDelegate for background searches on large documents. Implement didMatchString(_:) to receive each match and documentDidEndDocumentFind(_:) for completion.

Incremental Search and Find Interaction

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// Find next match from current selection
let next = document.findString("term", fromSelection: current, withOptions: [.caseInsensitive])

// System find bar; apply the Setup availability gate
pdfView.isFindInteractionEnabled = true

Text Extraction

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let fullText = document.string                          // Entire document
let firstPage = document.pageCount > 0 ? document.page(at: 0) : nil
let pageText = firstPage?.string                        // Single page
let attributed = firstPage?.attributedString            // With formatting

// Region-based extraction
if let page = firstPage {
    let selection = page.selection(for: CGRect(x: 50, y: 50, width: 400, height: 200))
    let text = selection?.string
}

Highlighting Search Results

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let results = document.findString("important", withOptions: [.caseInsensitive])
for selection in results { selection.color = .yellow }
pdfView.highlightedSelections = results

if let first = results.first {
    pdfView.setCurrentSelection(first, animate: true)
    pdfView.go(to: first)
}

Annotations

Annotations are created with PDFAnnotation(bounds:forType:withProperties:) and added to a PDFPage.

Highlight Annotation

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func addHighlight(to page: PDFPage, selection: PDFSelection) {
    let highlight = PDFAnnotation(
        bounds: selection.bounds(for: page),
        forType: .highlight, withProperties: nil
    )
    highlight.color = UIColor.yellow.withAlphaComponent(0.5)
    page.addAnnotation(highlight)
}

Text Note Annotation

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let note = PDFAnnotation(
    bounds: CGRect(x: 100, y: 700, width: 30, height: 30),
    forType: .text, withProperties: nil
)
note.contents = "This is a sticky note."
note.color = .systemYellow
note.iconType = .comment
page.addAnnotation(note)

Free Text Annotation

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let freeText = PDFAnnotation(
    bounds: CGRect(x: 50, y: 600, width: 300, height: 40),
    forType: .freeText, withProperties: nil
)
freeText.contents = "Added commentary"
freeText.font = UIFont.systemFont(ofSize: 14)
freeText.fontColor = .darkGray
page.addAnnotation(freeText)

Link Annotation

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let link = PDFAnnotation(
    bounds: CGRect(x: 50, y: 500, width: 200, height: 20),
    forType: .link, withProperties: nil
)
link.url = URL(string: "https://example.com")
page.addAnnotation(link)

// Internal page link
link.destination = PDFDestination(page: targetPage, at: .zero)

Removing Annotations

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for annotation in page.annotations {
    page.removeAnnotation(annotation)
}

Common subtypes include .highlight, .underline, .strikeOut, .text, .freeText, .ink, .link, .line, .square, .circle, .stamp, and .widget.

Thumbnails

PDFThumbnailView

PDFThumbnailView shows a strip of page thumbnails linked to a PDFView.

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let thumbnailView = PDFThumbnailView()
thumbnailView.pdfView = pdfView
thumbnailView.thumbnailSize = CGSize(width: 60, height: 80)
thumbnailView.layoutMode = .vertical
thumbnailView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(thumbnailView)

Generating Thumbnails Programmatically

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let thumbnail = page.thumbnail(of: CGSize(width: 120, height: 160), for: .mediaBox)

// All pages
let thumbnails = (0..<document.pageCount).compactMap {
    document.page(at: $0)?.thumbnail(of: CGSize(width: 120, height: 160), for: .mediaBox)
}

SwiftUI Integration

Wrap PDFView in a UIViewRepresentable for SwiftUI. PDF-specific wrappers that configure PDFView, pages, annotations, search, thumbnails, or overlays belong in this skill; route only generic representable lifecycle, layout, or SwiftUI state architecture questions to SwiftUI/UIKit interop guidance.

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import SwiftUI
import PDFKit

struct PDFKitView: UIViewRepresentable {
    let document: PDFDocument

    func makeUIView(context: Context) -> PDFView {
        let pdfView = PDFView()
        pdfView.autoScales = true
        pdfView.displayMode = .singlePageContinuous
        pdfView.document = document
        return pdfView
    }

    func updateUIView(_ pdfView: PDFView, context: Context) {
        if pdfView.document !== document {
            pdfView.document = document
        }
    }
}

Usage

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struct DocumentScreen: View {
    let url: URL

    var body: some View {
        if let document = PDFDocument(url: url) {
            PDFKitView(document: document)
                .ignoresSafeArea()
        } else {
            ContentUnavailableView("Unable to load PDF", systemImage: "doc.questionmark")
        }
    }
}

For interactive wrappers with page tracking, annotation hit detection, and coordinator patterns, see references/pdfkit-patterns.md.

Page Overlays

PDFPageOverlayViewProvider places UIKit views on top of individual pages for interactive controls or custom rendering beyond standard annotations.

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class OverlayProvider: NSObject, PDFPageOverlayViewProvider {
    func pdfView(_ view: PDFView, overlayViewFor page: PDFPage) -> UIView? {
        let overlay = UIView()
        // Add custom subviews
        return overlay
    }
}

class PDFOverlayController: UIViewController {
    let pdfView = PDFView()
    private let overlayProvider = OverlayProvider()

    override func viewDidLoad() {
        super.viewDidLoad()
        pdfView.pageOverlayViewProvider = overlayProvider
    }
}

pageOverlayViewProvider is weak, so keep the provider strongly owned. For overlay lifecycle and save handling, read references/pdfkit-patterns.md.

Common Mistakes

DON'T: Force-unwrap PDFDocument init

PDFDocument(url:) and PDFDocument(data:) are failable initializers.

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// WRONG
let document = PDFDocument(url: url)!

// CORRECT
guard let document = PDFDocument(url: url) else { return }

DON'T: Forget autoScales on PDFView

Without autoScales, the PDF renders at its native resolution.

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// WRONG
pdfView.document = document

// CORRECT
pdfView.autoScales = true
pdfView.document = document

DON'T: Ignore PDF coordinate system in annotations

PDF page coordinates have origin at the bottom-left with Y increasing upward -- opposite of UIKit.

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// WRONG: UIKit coordinates
let bounds = CGRect(x: 50, y: 50, width: 200, height: 30)

// CORRECT: PDF coordinates (origin bottom-left)
let pageBounds = page.bounds(for: .mediaBox)
let pdfY = pageBounds.height - 50 - 30
let bounds = CGRect(x: 50, y: pdfY, width: 200, height: 30)

DON'T: Modify annotations on a background thread

PDFKit classes are not thread-safe.

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// WRONG
DispatchQueue.global().async { page.addAnnotation(annotation) }

// CORRECT
DispatchQueue.main.async { page.addAnnotation(annotation) }

DON'T: Compare PDFDocument with == in UIViewRepresentable

PDFDocument is a reference type. Use identity (!==).

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// WRONG: Always replaces document
func updateUIView(_ pdfView: PDFView, context: Context) {
    pdfView.document = document
}

// CORRECT
func updateUIView(_ pdfView: PDFView, context: Context) {
    if pdfView.document !== document {
        pdfView.document = document
    }
}

Review Checklist

• PDFDocument init uses optional binding, not force-unwrap
• pdfView.autoScales = true set for proper initial display
• Page indices checked against pageCount before access
• displayMode and displayDirection configured to match design
• Annotations use PDF coordinate space (origin bottom-left, Y up)
• All PDFKit mutations happen on the main thread
• Password-protected PDFs handled with isLocked / unlock(withPassword:)
• SwiftUI wrapper uses !== identity check in updateUIView
• PDFViewPageChanged notification observed for page tracking
• PDFThumbnailView.pdfView linked to the main PDFView
• Large-document search uses async beginFindString with delegate
• Saved documents use write(to:withOptions:) when encryption needed

References

• Extended patterns (forms, watermarks, merging, printing, overlays, outlines, custom drawing): references/pdfkit-patterns.md
• PDFKit framework
• PDFView
• PDFDocument
• PDFPage, PDFAnnotation, PDFSelection, PDFThumbnailView
• PDFPageOverlayViewProvider
• Adding Widgets to a PDF Document
• Adding Custom Graphics to a PDF