Erro com pdf_get_buffer na PDFlib do PHP !

Boa tarde galera, alguém pode me ajudar de novo?

To com um problema chato de BUFFER !!! Pq esse comando ñ dá certo ?!

$data = pdf_get_buffer($pdf);

Código:

<?php$pdf = pdf_new();pdf_open_file($pdf);pdf_begin_page($pdf, 595, 842);pdf_set_font($pdf, "Times-Roman", 30, "host");pdf_set_value($pdf, "textrendering", 1);pdf_show_xy($pdf, "A PDF document created in memory!", 50, 750);pdf_end_page($pdf);pdf_close($pdf);$data = pdf_get_buffer($pdf);header("Content-type: application/pdf");header("Content-disposition: inline; filename=test.pdf");header("Content-length: " . strlen($data));echo $data;?>O erro é o seguinte:

Fatal error: Uncaught exception 'PDFlibException' with message 'pdf_open_file() expects exactly 2 parameters, 1 given' in C:\PHP\Apache\htdocs\teste_pdf.php:5 Stack trace: #0 C:\PHP\Apache\htdocs\teste_pdf.php(5): pdf_open_file(Resource id #2) #1 {main} thrown in C:\PHP\Apache\htdocs\teste_pdf.php on line 5Help-me !!! Denovo ... rsrsrs