function tncsupport_change_categories_label($translated_text, $text, $domain) {
    if ($text === 'Categories' && $domain === 'display-pdf-viewer-for-wordpress-addon') {
        return 'Custom Text'; // Replace this with the desired text.
    }
    return $translated_text;
}
add_filter('gettext', 'tncsupport_change_categories_label', 10, 3);