class ResourceFile extends DataObject {
   static $db = array (
      'Name' => 'Text',
      'Description' => 'Text',
   );
   
   static $has_one = array (
      'pdf' => 'PdfFile',
      'DocumentsPage' => 'DocumentsPage'
   );
   
   public function getCMSFields_forPopup() {
      $pdfFile = new FileIFrameField('pdf');
      $pdfFile->setAllowedExtensions(array('pdf'));
      
      return new FieldSet(
         new TextField('Name'),
         new TextareaField('Description'),
         $pdfFile,
      );
   }
}

class DocumentsPage extends Page {

   static $has_many = array(
      'Documents' => 'ResourceFile'
   );
   
   public function getCMSFields() {
      $f = parent::getCMSFields();
      $manager = new FileDataObjectManager(
         $this, // Controller
         'Documentss', // Source name
         'ResourceFile', // Source class
         'pdf', // File name on DataObject
         array(
            'Name' => 'Name',
            'Description' => 'Description',
         ), // Headings
         'getCMSFields_forPopup' // Detail fields (function name or FieldSet object)
         // Filter clause
         // Sort clause
         // Join clause
      );
$manager->setBrowseButtonText("Upload (pdf only)");
$manager->setAllowedFileTypes(array('pdf'));
                  
      $f->addFieldToTab("Root.Content.Documents",$manager);

      return $f;
   }
}

class DocumentsPage_Controller extends Page_Controller {
}

class PdfFile extends File {
   function BackLinkTracking() {
      return false;
   }
}