PDFKit Core Implementation Details

import PDFKit

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)
        }
    }
}

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

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

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

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

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)
}

// 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)
}

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)"
}

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

// 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

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
}

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)
}

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)
}

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)

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)

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)

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

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

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)
}

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
        }
    }
}

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")
        }
    }
}

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
    }
}