code: public PdfDictionary getSignatureDictionary(String name) {
          getSignatureNames();
          name = getTranslatedFieldName(name);
          if (!sigNames.containsKey(name))
              return null;
          Item item = (Item)fields.get(name);
          PdfDictionary merged = item.getMerged(0);
          return merged.getAsDict(PdfName.V);
      }
docs: Gets the signature dictionary, the one keyed by /V.
  
  @param name the field name
  @return the signature dictionary keyed by /V or <CODE>null</CODE> if the field is not
  a signature