TextProperties textProperties = new TextProperties();
textProperties.textSize = 24;
textProperties.typeface = Typeface.create(Typeface.DEFAULT, Typeface.BOLD);
textProperties.alignment = Layout.Alignment.ALIGN_CENTER;

TextComposer textComposer = new TextComposer(simplyPdfDocument);
textComposer.write("SimplyPDF", textProperties);