Add content after every post with a plugin – WP Hooks

Inside wp-content/plugins folder create a new file called pixaty-hooks.php and paste the below code.

<?php
/**
 * Plugin Name: pixalty-hooks
 * Description: A simple plugin to demonstrate how to use hooks in WordPress.
 * Version: 1.0
 */

add_filter( 'the_content', 'pixalty_amend_content' );

function pixalty_amend_content( $content ) {
    return $content . '<p>Thanks for reading!(YOUR CONTENT HERE)</p>';
}