Polish vowels in PDF

Using moodle in Polish language so, writing item contents in Polish, causes the pdf of a single response with special chars like: ąčęėįšųūž to be reported as ????????.
Changing the PDF font to freesans, seems to fix the problem.

Reference: https://stackoverflow.com/questions/5333702/tcpdf-utf-8-symbols-not-showing-up?rq=4

classes/submissions_list.php

@@ -1806,7 +1806,7 @@ private function replace_http_url($content) {
      * @return void
      */
     private function add_pdf_details($pdf, $user, $timecreated, $timemodified) {
-        $pdf->SetFont('helvetica', '', 12);
+        $pdf->SetFont('freesans', '', 12);
 
         // Set document information.
         $pdf->SetCreator(PDF_CREATOR);