Ya. I actually found it in one of their demos. But just in case anyone needs to reference that, you add the css drop down as follows:

$editor->set_stylesheet($settings->main['general']['baseURL']."/include/pageStyles.css");
$editor->set_classmenu(array(
'text1' => 'text1',
'text2' => 'text2',
'text3' => 'text3',
'heading1' => 'heading1',
'heading2' => 'heading2',
'heading3' => 'heading3',
));

First line assign the css file. Second+ lines add the styles.