code: function putCatalogCallback() {
      // Put reference to AcroForm to DocumentCatalog
      if (typeof scope.internal.acroformPlugin.acroFormDictionaryRoot != 'undefined') {
        // for safety, shouldn't normally be the case
        scope.internal.write('/AcroForm ' + scope.internal.acroformPlugin.acroFormDictionaryRoot.objId + ' ' + 0 + ' R');
      } else {
        throw new Error('putCatalogCallback: Root missing.');
      }
    }
docs: Callbacks