code: public static void moveFields(PdfDictionary from, PdfDictionary to) {
          for (Iterator i = from.getKeys().iterator(); i.hasNext();) {
              PdfName key = (PdfName)i.next();
              if (fieldKeys.containsKey(key)) {
                  if (to != null)
                      to.put(key, from.get(key));
                  i.remove();
              }
          }
      }
docs: Moves the field keys from <CODE>from</CODE> to <CODE>to</CODE>. The moved keys
  are removed from <CODE>from</CODE>.
  @param from the source
  @param to the destination. It may be <CODE>null</CODE>