pdflib greek problem

Hi, I am trying the following code to generate a pdf: try {

       // Create a new pdf handler
       $pdf = new PDFlib();

       //  open new PDF file
       if ($pdf->begin_document("", "") == 0) {
           die("Error: " . $p->get_errmsg());
       }

       // Set some info to the new pdf
       $pdf->set_info("Creator", "Test");
       $pdf->set_info("Author", "Test");
       $pdf->set_info("Title", "Test");
             // Start the page
       $pdf->begin_page_ext(595, 842, "");
             // Load the documents font and set the details
       $font = $pdf->load_font("Times-Roman", "iso8859-7", "");
       $pdf->setfont($font,24.0);
       $pdf->set_parameter('autospace',TRUE);
             // Set the position inside the document
       $pdf->set_text_pos(50, 700);
             // Now start to show the data
       $str = 'Αυτό είναι ένα τεστ.';
       mb_convert_variables('ISO-8859-7','UTF-8',$str);
       $pdf->show($str);
             // End the page and the document
       $pdf->end_page_ext("");
       $pdf->end_document("");
             // Get the document from the buffer find it's length
       $buf = $pdf->get_buffer();
       $len = strlen($buf);
             // And finally print it out to the browser
       header("Content-type: application/pdf");
       header("Content-Length: $len");
       header("Content-Disposition: inline; filename=hello.pdf");
       print $buf;
           }
     catch (PDFlibException $e) {
       die("PDFlib exception occurred in hello sample:\n" .

"[" . $e->get_errnum() . "] " . $e->get_apiname() . ": " .

       $e->get_errmsg() . "\n");

} catch (Exception $e) {

       die($e);

} Although greek are printed normally the characters are overlapping on each other. The script in encoded in UTF-8. Does anybody have any suggestions on this? Please any help would be appreciated. -- Thodoris