JordanCoin/ios-skills-collection

PDFKit

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

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.

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 (0-based)
let count = document.pageCount
document.insert(PDFPage(), at: count)
document.removePage(at: 2)
document.exchangePage(at: 0, withPageAt: 3)

Page Navigation

PDFView provides built-in navigation with history tracking.

// Go to a specific page
if let page = pdfView.document?.page(at: 5) {
    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 a page
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 pageText = document.page(at: 0)?.string             // Single page
let attributed = document.page(at: 0)?.attributedString  // With formatting

// Region-based extraction
if let page = document.page(at: 0) {
    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)
}

Annotation Subtypes Reference

Subtype	Constant	Purpose
Highlight	.highlight	Text markup (yellow highlight)
Underline	.underline	Text markup (underline)
StrikeOut	.strikeOut	Text markup (strikethrough)
Text	.text	Sticky note icon
FreeText	.freeText	Inline text block
Ink	.ink	Freehand drawing paths
Link	.link	URL or page destination
Line	.line	Straight line with endpoints
Square	.square	Rectangle shape
Circle	.circle	Ellipse shape
Stamp	.stamp	Rubber stamp (Approved, etc.)
Widget	.widget	Form element (text field, checkbox)

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.

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
    }
}

pdfView.pageOverlayViewProvider = overlayProvider

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