Adding metadata and keywords to PDF using JasperReports

Question

I want to add some Keywords to my pdf-file via the PdfExporterConfiguration but don’t want to manipulate other values.
By creating a new SimplePdfExporterConfiguration,
adding it to the JRPdfExporter all configurations seem to be lost.
Is it possible to get the default PdfExporterConfiguration from a JRPdfExporter or the default values?

I’m using JasperReports 6.3.0

My current code:

file = File.createTempFile("tempfile", ".tmp");
fos = new FileOutputStream(file);
JasperReport jr = JasperCompileManager.compileReport(rt.getLocation());
JasperPrint jp = JasperFillManager.fillReport(jr, params);

SimplePdfExporterConfiguration config = new SimplePdfExporterConfiguration();
config.setMetadataKeywords("/sgnsignatures {1} /sgnsignature_1 {1 0 10 10 150 30} /sgnsigner_1 {customer}");

JRPdfExporter pdfExporter = new JRPdfExporter();
pdfExporter.setExporterInput(new SimpleExporterInput(jp));
pdfExporter.setExporterOutput(new SimpleOutputStreamExporterOutput(fos));
pdfExporter.setConfiguration(config);
pdfExporter.exportReport();