magento1.9 _prepareDownloadResponse multiple pdf download

i want to multiple pdf download on same controller

default code :

return $  this->_prepareDownloadResponse(   'docs'.Mage::getSingleton('core/date')->date('Y-m-d_H-i-s').'.pdf',$  pdf->render(), 'application/pdf'); 

here download one pdf file i want to add new pdf file in this retrun code

Any help would be appreciated.

Thanks.