[TIMOB-25680] iOS 11.2: DocumentViewer not displaying PDF files (Apple regression)

   var win = Ti.UI.createWindow({
     backgroundColor: '#fff'
   });
   
   var btn = Ti.UI.createButton({
     title: 'Open PDF'
   });
   
   btn.addEventListener('click', function(e) {
     var docViewer = Ti.UI.iOS.createDocumentViewer({
       url : 'example.pdf'
     });
    
     docViewer.show();
   });
   
   win.add(btn);
   win.open();
   

   var win = Ti.UI.createWindow({
     backgroundColor: '#fff'
   });
   
   var btn = Ti.UI.createButton({
     title: 'Open PDF'
   });
   
   btn.addEventListener('click', openPDF);
   
   win.add(btn);
   win.open();
   
   // Open the PDF file
   function openPDF() {
     var fileName = 'example.pdf';
     
     // For iOS 11.2, workaround the Apple issue by creating a temporary file and
     // reference it. It will be removed from filesystem once the app closes.
     // Read more here: http://nshipster.com/nstemporarydirectory/
     if (isiOS11_2()) {
       fileName = fileInTemporaryDirectory(fileName);
     }
     
     var docViewer = Ti.UI.iOS.createDocumentViewer({
       url: fileName
     });
    
     docViewer.show();
   }
   
   // Check if the current device runs iOS 11.2+
   function isiOS11_2() {
   	var version = Ti.Platform.version.split(".");	
   	return (parseInt(version[0]) >= 11 && parseInt(version[1]) >= 2);
   }
   
   // Create a temporary file with the contents of the old file
   // Expects the file to be in the resources directory. If you receive the file 
   // from an API-call, receive pass the Ti.Blob/Ti.File/text to "write" directly.
   function fileInTemporaryDirectory(fileName) {
     var file = Ti.Filesystem.getFile(Ti.Filesystem.resourcesDirectory, fileName);
     
     if (!file.exists()) {
       alert('File does not exist in resources!');
       return;
     }
     
     var newFile = Titanium.Filesystem.getFile(Ti.Filesystem.tempDirectory, fileName);
     newFile.createFile();
     
     if (!newFile.exists()) {
       alert('New file could not be created in temporary directory!');
       return;
     }
     
     newFile.write(file);
     
     return newFile.nativePath;
   }