pdfkit

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SKILL.md

Full skill instructions

PDFKit

Display, navigate, search, annotate, and manipulate PDF documents with PDFView, PDFDocument, PDFPage, PDFAnnotation, and PDFSelection. Targets Swift 6.3 / iOS 26+.

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.

import PDFKit

Platform availability: iOS 11+, iPadOS 11+, Mac Catalyst 13.1+, macOS 10.4+, tvOS 11+, visionOS 1.0+.

Displaying PDFs

PDFView is a UIView subclass that renders PDF content, handles zoom, scroll, text selection, and page navigation out of the box.

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

Mode	Behavior
`.singlePage`	One page at a time
`.singlePageContinuous`	Pages stacked vertically, scrollable
`.twoUp`	Two pages side by side
`.twoUpContinuous`	Two-up with continuous scrolling

Scaling and Appearance

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.

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

Password-Protected PDFs

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

Saving and Page Manipulation

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.

// 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

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

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

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

// System find bar (iOS 16+)
pdfView.isFindInteractionEnabled = true

Text Extraction

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

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

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

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

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

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

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.

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

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.

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

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 (iOS 16+)

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

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.

// 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.

// 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.

// 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.

// 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 (!==).

// 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

Install skill

Copy and run in your terminal

npx -y skills add https://github.com/dpearson2699/swift-ios-skills --skill pdfkit

View on GitHub

pdfkit

pdfkit

SKILL.md

PDFKit

Contents

Setup

Displaying PDFs

Display Modes

Scaling and Appearance

Loading Documents

Password-Protected PDFs

Saving and Page Manipulation

Page Navigation

Observing Page Changes

Text Search and Selection

Synchronous Search

Asynchronous Search

Incremental Search and Find Interaction

Text Extraction

Highlighting Search Results

Annotations

Highlight Annotation

Text Note Annotation

Free Text Annotation

Link Annotation

Removing Annotations

Thumbnails

PDFThumbnailView

Generating Thumbnails Programmatically

SwiftUI Integration

Usage

Page Overlays (iOS 16+)

Common Mistakes

DON'T: Force-unwrap PDFDocument init

DON'T: Forget autoScales on PDFView

DON'T: Ignore PDF coordinate system in annotations

DON'T: Modify annotations on a background thread

DON'T: Compare PDFDocument with == in UIViewRepresentable

Review Checklist

References