title: UIDocumentInteractionController and PDF
body: <p>I can successfully open png files, but when I try to open pdf, the preview says "Portable Document Format" without showing the content.</p>
  
  <pre><code>    self.docInteractionController.UTI = @"com.adobe.pdf";
  
      if ([operation isEqualToString:@"open"])
  
          if (![self.docInteractionController presentPreviewAnimated:YES])
                NSLog(@"Failed to open document in Document Dir");
  </code></pre>
  
  <p>Any hint?</p>