How can I add pager to the comments of advanced forum in drupal 7?
In your style directory, you should have a *.topic-header.tpl.php file. Make sure the following is where you want the paging to display:

&lt;?php print($pager); ?&gt;


Then, in *sites/all/modules/advanced_forum/includes/theme.inc*

Approximately line 446:

  pager_default_initialize($variables['node']-&gt;comment_count, variable_get('comment_default_per_page_forum'));
  $variables['pager'] = theme('pager');