Display content from another site page using a shortcode

You can create a shortcode as below:

function wpse250662_post_content_shortcode($atts) {

    $args = shortcode_atts( array(
        'pagename' => ''
    ), $atts );

    $query = new WP_Query( $args );

    if ( $query->have_posts() ) :
        while ( $query->have_posts() ) : $query->the_post();
            $content = apply_filters('the_content',get_the_content( ));
            ob_start();
            ?>
            <div class="content">
                <?php echo $content; ?>
            </div>
            <?php
        endwhile;
    endif;
    wp_reset_postdata();
    return ob_get_clean();
}
add_shortcode('wpse250662-content', 'wpse250662_post_content_shortcode');

USAGE:

[wpse250662-content pagename="PAGE SLUG YOU WANT TO DISPLAY"]

Resources: Shortcode API