code: public void setExport(boolean export) {
          PdfDictionary usage = getUsage();
          PdfDictionary dic = new PdfDictionary();
          dic.put(PdfName.EXPORTSTATE, export ? PdfName.ON : PdfName.OFF);
          usage.put(PdfName.EXPORT, dic);
      }
docs: Specifies the recommended state for content in this
  group when the document (or part of it) is saved by a viewer application to a format
  that does not support optional content (for example, an earlier version of
  PDF or a raster image format).
  @param export the export state