use the HTML Mime Mail class

try downloading HTML Mime Mail class from http://www.heyes-computing.net/scripts/ (I use version 1.33)

in the end somewhere of your pdf-script you have something like this:
//
PDF_close($p);

$buf = PDF_get_buffer($p);
$len = strlen($buf);
//

use the $buf variable as the attachment on the line from the script as shown:

$mail->add_attachment($buf, "Presentationer_1_per_sida.pdf", 'application/octet-stream');

This works fine form me.

/Jesper