title: How do I mark an IBOutlet as available for a specific iOS version
body: <p>I am using the PDFKit native framework which is available for iOS 11 only and my project targets older iOS versions.
  Xcode asked me to mark the whole <code>UIViewController</code> class as <code>@available(iOS 11.0, *)</code></p>
  
  <p>I'd like to handle viewing the PDF on older iOS versions in the same <code>UIViewController</code> using a different <code>UIView</code> that's going to use a <code>UIWebView</code> or a 3rd party library. How can I achieve that?</p>