Try this
Output("", "S");
$attachment = chunk_split(base64_encode($pdfdoc));
///////////HEADERS INFORMATION////////////
// main header (multipart mandatory) message
$headers = "From: Sender_Name".$eol;
$headers .= "Bcc: email@domain.com".$eol;
$headers .= "MIME-Version: 1.0".$eol;
$headers .= "Content-Type: multipart/mixed; boundary=\"".$separator."\"".$eol.$eol;
$headers .= "Content-Transfer-Encoding: 7bit".$eol;
$headers .= "This is a MIME encoded message.".$eol.$eol;
// message
$headers .= "--".$separator.$eol;
$headers .= "Content-Type: text/html; charset=\"iso-8859-1\"".$eol;
$headers .= "Content-Transfer-Encoding: 8bit".$eol.$eol;
$headers .= $message.$eol.$eol;
// attachment
$headers .= "--".$separator.$eol;
$headers .= "Content-Type: application/octet-stream; name=\"".$filename."\"".$eol;
$headers .= "Content-Transfer-Encoding: base64".$eol;
$headers .= "Content-Disposition: attachment".$eol.$eol;
$headers .= $attachment.$eol.$eol;
$headers .= "--".$separator."--";
//Email message
mail($emailto, $emailsubject, $emailbody, $headers);
?>