How do I add classes to read-more link and add-comment link on node for bootstrap 3
You were very close except at the end of your first line you had a "." instead of a ";".

function meetu_preprocess_node(&amp;$variables) {
  $variables['content']['links']['node']['#links']['node-readmore']['attributes']['class'][] = 'btn btn-primary';
  $variables['content']['links']['node']['#links']['comment-add']['attributes']['class'][] = 'btn btn-primary';
}