how to write UTF-8 (persian) characters in pdf export of dynamic reports?

I'm trying to export a report to pdf format using dynamic reports but the persian characters do not appear in pdf file. but I don't have this problem in xls files or jasper viewer. i have tried this method but it doesn't work. what should i do?

public void toPdf(String path){
    JasperPdfExporterBuilder pdfExporter = new ExporterBuilders()
    .pdfExporter(path);
    pdfExporter.setCharacterEncoding("UTF-8");
    try {

        jasperReportBuilder.toPdf(pdfExporter);
    } catch (Exception e1) {
        logger.error("failed to create PDF", e1);
    }
}

excel export :

jasper viewer :

PDF export :