writer.setViewerPreferences(PdfWriter.PageModeUseOC);
// step 3
document.open();
// step 4
PdfContentByte cb = writer.getDirectContent();
LwgPhrase explanation = new LwgPhrase("Ordered layers", new LwgFont(
LwgFont.HELVETICA, 20, LwgFont.BOLD, Color.red));
ColumnText.showTextAligned(cb, LwgElement.ALIGN_LEFT, explanation, 50,
650, 0);
PdfLayer l1 = new PdfLayer("Layer 1", writer);
PdfLayer l2 = new PdfLayer("Layer 2", writer);