JODConverter.java

public class JODConverter {

    private static volatile OfficeManager officeManager;
    private static volatile OfficeDocumentConverter converter;

    public static void startOfficeManager(){
        try {

            officeManager = new DefaultOfficeManagerConfiguration()
                    .setOfficeHome(new File('libre office home path'))
                    .setPortNumbers(8100, 8101, 8102, 8103, 8104 )  
                    .setTaskExecutionTimeout(600000L)    // for big files
                    .setTaskQueueTimeout(200000L)        // wait if all port were busy
                    .buildOfficeManager();
            officeManager.start();

            // 2) Create JODConverter converter
            converter = new OfficeDocumentConverter(officeManager);

        } catch (Throwable e){
            e.printStackTrace();
        }
    }

    public static void convertPDF(File inputFile, File outputFile) throws Throwable {

        converter.convert(inputFile, outputFile);
    }

    public static void stopOfficeManager(){
        officeManager.stop();
    }

}