/**
  * Attach factory to the current;
  *
  * @param Zend_Pdf_ElementFactory $factory
  */
 public function attach(Zend_Pdf_ElementFactory $factory)
 {
     if ($factory == $this || isset($this->_attachedFactories[$factory->getId()])) {
         /**
          * Don't attach factory twice.
          * We do not check recusively because of nature of attach operation
          * (Pages are always attached to the Documents, Fonts are always attached
          * to the pages even if pages already use Document level object factory and so on)
          */
         return;
     }
     $this->_attachedFactories[$factory->getId()] = $factory;
 }