$fd = fopen("./diploma.pdf", "w");
$pdf = PDF_new();
PDF_open_file($pdf,"./diploma.pdf");
PDF_begin_page($pdf,660,550);
$fuente = PDF_load_font($pdf,"Helvetica-Bold","iso8859-1","");
pdf_setfont ( $pdf, $fuente, 15 );
PDF_show($pdf,"CERTIFICADO DE APROVECHAMIENTO");
PDF_end_page($pdf);
PDF_close($pdf);
fclose($fd);