Maybe use this on the order_done.php
<h1><?php echo JText::_('COM_VIRTUEMART_ACC_ORDER_INFO'); ?>
<?php
/* Print view URL */
$details_url = juri::root().'index.php?option=com_virtuemart&view=orders&layout=details&tmpl=component&virtuemart_order_id=' . $this->orderdetails['details']['BT']->virtuemart_order_id .'&order_pass=' . JRequest::getString('order_pass',false) .'&order_number='.JRequest::getString('order_number',false);
$details_link = "<a href=\"javascript:void window.open('$details_url', 'win2', 'status=no,toolbar=no,scrollbars=yes,titlebar=no,menubar=no,resizable=yes,width=640,height=480,directories=no,location=no');\" >";
//$details_link .= '<span class="hasTip print_32" title="' . JText::_('COM_VIRTUEMART_PRINT') . '"> </span></a>';
$button = (JVM_VERSION==1) ? '/images/M_images/printButton.png' : 'system/printButton.png';
$details_link .= JHtml::_('image',$button, JText::_('COM_VIRTUEMART_PRINT'), NULL, true);
$details_link .= '</a>';
echo $details_link; ?>
</h1>