Paginate Child Pages

paginate-child-pages.php

function paginate_child_pages( $post ) {
  $page_id = $post->ID;
  
  $args = array(
    'post_type'      => 'page',
    'posts_per_page' => -1,
    'post_parent'    => $page_id,
    'order'          => 'ASC', //change to fit your order
    'orderby'        => 'menu_order', //change to fit your order
 	);


	$child_pages = new WP_Query( $args );

	if ( $child_pages->have_posts() ) {
		$pagination = '<ul class="pages">\n';
			$format = '\t<li><a href="%1$s">%2$s</a></li>\n';
		$counter = 0;
		while ( $parent->have_posts() ) {
			$parent->the_post();
			$counter++;
			$pagintation .= sprintf( $format, get_the_permalink(), $counter );
		}
		$pagination .= '</ul>';

	} 

	wp_reset_postdata();

	return $pagination;
  
}

Caveats:

• This is quick, dirty, and untested.
• You probably don't need to pass $post. You can make the first line of the function global $post;
• You'll almost definitely run into string literal issues with the \t and \n within single quotes.
• This returns a string that can then be printed.