title: iOS PDFKit - width issue
body: <p>In my app I'm using PDFKit to display simple PDF's. </p>
  
  <p>A PDF is presented on a ViewController. The PDF to be set to the width of the screen and no more. I set a constraint in storyboard for PDFView to be 'equal width to superview'. If the PDF is over multiple pages so the user can scroll vertically.</p>
  
  <p>All seemed to be fine, works perfectly on all screen sizes expect iPhone SE / 5, where the PDF width is greater than the screen size and thus requires a horizontal scroll to view the whole document.</p>
  
  <p>Not sure why the PDFView is greater width than the screen view when I've set a constraint 'equal width to superview'</p>
  
  <p>Below is the code from one of my view controllers that presents a PDF</p>
  
  <pre><code>import Foundation
  import UIKit
  import PDFKit
  
  class DisclaimerViewController: UIViewController, UIScrollViewDelegate {
  
  
  @IBOutlet var pdfView: PDFView!
  
  
  
  override func viewDidLoad() {
      super.viewDidLoad()
  
      if let path = Bundle.main.path(forResource: "Disclaimer", ofType: "pdf") {
          let url = URL(fileURLWithPath: path)
          if let pdfDocument = PDFDocument(url: url) {
  
  
              pdfView.document = pdfDocument
              pdfView.autoScales = true
              pdfView.maxScaleFactor = 4.0
              pdfView.minScaleFactor = pdfView.scaleFactorForSizeToFit
              pdfView.displayMode = .singlePageContinuous
  
  
          }
      }
  
      // colour scheme
  
      //navigationController?.navigationBar.barTintColor = UIColor(red:0.6, green:0.4, blue:1.0, alpha:1.0)
      self.view.backgroundColor = UIColor.black
  }
  
  
  
  
  
  override var preferredStatusBarStyle : UIStatusBarStyle {
      return UIStatusBarStyle.lightContent
  }
  
  override func didReceiveMemoryWarning() {
      super.didReceiveMemoryWarning()
      // Dispose of any resources that can be recreated.
  }
  
  override func viewWillAppear(_ animated: Bool) {
      super.viewWillAppear(animated)
  
  
  }
  
  @IBAction func back(_ sender: AnyObject) {
  
  
      self.dismiss(animated: true, completion: nil)
  }
  </code></pre>
  
  <p>} </p>
  
  <p>Please note this is testing in simulator. Is this simulator bug? Or am I missing something?</p>
  
  <p>Thanks in advance</p>