* @throws IOException on error
     * @throws DocumentException on error
     */
    public void setFields(FdfReader fdf) throws IOException, DocumentException {
        HashMap<String, PdfDictionary> fd = fdf.getFields();
        for (String f: fd.keySet()) {
            String v = fdf.getFieldValue(f);
            if (v != null)
                setField(f, v);
        }
    }