Create Custom Sidebar

custom-sidebar.php

<?php
/*
 * Create Custom Widget Area for Pages Only
 */
function page_only_custom_sidebar() {
    register_sidebar(
        array (
            'name'          => __( 'For Pages Only', 'your-site' ),
            'id'            => 'page-only-custom-sidebar',
            'description'   => __( 'Contents to this widget area will be displayed on pages only.', 'your-site' ),
            'before_widget' => '<section id="%1$s" class="widget %2$s">',
            'after_widget'  => "</section>",
            'before_title'  => '<h3 class="widget-title">',
            'after_title'   => '</h3>',
        )
    );
}
add_action( 'widgets_init', 'page_only_custom_sidebar' );
?>