title: "Cannot assign value of type 'Void' to type 'PDFAction?'" error when setting an action for a PDFAnnotation
body: <p>In my PDF Viewer app, I successfully opened a PDF and displayed all of its content. The PDF the app will always display is quite large with 130 pages. In the second page of the PDF, there is a table of contents. I want to add a <code>PDFButton</code> to the text and scroll to the correct page in the PDF the user has selected.</p>
  
  <p>My current code displays a button, but the action I want the button to perform results in an error:</p>
  
  <blockquote>
    <p>Cannot assign value of type 'Void' to type 'PDFAction?'</p>
  </blockquote>
  
  <p>Here is the code I have tried:</p>
  
  <pre><code>func insertResetButtonInto(_ page: PDFPage, GoTo: PDFPage) {
      let resetButtonBounds = CGRect(x: 90, y: 200, width: 200, height: 15)
      let resetButton = PDFAnnotation(bounds: resetButtonBounds, forType: PDFAnnotationSubtype(rawValue: PDFAnnotationSubtype.widget.rawValue), withProperties: nil)
      resetButton.widgetFieldType = PDFAnnotationWidgetSubtype(rawValue: PDFAnnotationWidgetSubtype.button.rawValue)
      resetButton.widgetControlType = .pushButtonControl
      resetButton.backgroundColor = UIColor.green
      page.addAnnotation(resetButton)
  
      // Create PDFActionResetForm action to clear form fields.
      resetButton.action = pdfView.go(to: page)
  }
  </code></pre>
  
  <p>How can I create a button in the PDF that works as a sequence or a scrolling function that takes the user to a different page in the same PDF document?</p>