Pre-populating new Page creation with shortcodes

You can add any default content you like, but I don’t know of a way of doing it just for Pages (the following will apply to both Pages and Posts):

add_filter( 'default_content', 'my_default_post_content' );

function my_default_post_content( $content ) {
    $content = "Hello World!";
    return $content;
}

(place this in your functions.php file)