bbPress.org

bbPress and BuddyPress include the pagination at the top and bottom by default.

Your custom theme appears to not do that, most likely the template you need to edit is either content-single-topic.php or content-single-topic-lead.php and look for something similar to:

<?php bbp_get_template_part( 'pagination', 'replies' ); ?>

<?php bbp_get_template_part( 'loop',       'replies' ); ?>

And change that to:

<?php bbp_get_template_part( 'pagination', 'replies' ); ?>

<?php bbp_get_template_part( 'loop',       'replies' ); ?>

<?php bbp_get_template_part( 'pagination', 'replies' ); ?>

If your not comfortable doing that then contact the theme author for details.