Show 'previous' and 'next' links on current page:
<?php
$pages_args = array(
'child_of' => $post->post_parent,
'parent' => $post->post_parent,
'sort_column' => 'menu_order,post_title',
'sort_order' => 'asc'
);
$page_list = get_pages($pages_args);
$pages = array();
foreach ($page_list as $page) {
$pages[] += $page->ID;
}
$current_num = array_search($post->ID, $pages);
$prev_id = $pages[$current_num - 1];
$next_id = $pages[$current_num + 1];
?>
<ul class="nav-wrap">
<?php if (!empty($prev_id)) : ?>
<li class="nav-prev">
<a href="<?php echo get_permalink($prev_id); ?>">Previous: <?php echo get_the_title($prev_id); ?></a>
</li>
<?php endif;
if (!empty($next_id)) : ?>
<li class="nav-next">
<a href="<?php echo get_permalink($next_id); ?>">Next: <?php echo get_the_title($next_id); ?></a>
</li>
<?php endif; ?>
</ul>