Just put it before the if statement, like this:

Code:
$tmpt[0][7]=strip_tags($tmpt[0][7]); 
$tmpt[0][7]=htmlspecialchars_decode($tmpt[0][7],ENT_QUOTES);
if ($countproductsonpo != $countproducts)
$pdf->addNotes(SHIPPING_OPTION.": ".$tmpt[0][7]."\n\n".PO_PARTIALSHIP_PACKINGLIST."\n".$_POST[plistcomments]);        
else
 $pdf->addNotes(SHIPPING_OPTION.": ".$tmpt[0][7]."\n\n".PO_FULLSHIP_PACKINGLIST."\n".$_POST[plistcomments]);
$pdf->Output(PO_PACKINGLIST_FILENAME, "F");
 if ($_POST[reviewthensend] == 'yes') {
 ?>