Example:

Document doc = new Document();

// Insert text that spans 16 pages.
DocumentBuilder builder = new DocumentBuilder(doc);
builder.writeln("My Booklet:");

for (int i = 0; i < 15; i++) {
    builder.insertBreak(BreakType.PAGE_BREAK);
    builder.write(MessageFormat.format("Booklet face #{0}", i));
}

// Configure the first section's "PageSetup" property to print the document in the form of a book fold.
// When we print this document on both sides, we can take the pages to stack them
// and fold them all down the middle at once. The contents of the document will line up into a book fold.
PageSetup pageSetup = doc.getSections().get(0).getPageSetup();
pageSetup.setMultiplePages(MultiplePagesType.BOOK_FOLD_PRINTING);

// We can only specify the number of sheets in multiples of 4.
pageSetup.setSheetsPerBooklet(4);

doc.save(getArtifactsDir() + "PageSetup.Booklet.docx");