How do I reverse the order of submit and preview button?
One solution is to use hook_form_alter() in a custom module to make the submit button heavier than the preview button:

function MYMODULE_form_alter(&amp;$form, &amp;$form_state, $form_id) {

  if($form_id == 'MYNODETYPE_node_form') {
    $form['actions']['preview']['#weight'] = $form['actions']['submit']['#weight']-1;
  }
}


Just change the module name and form id accordingly.