How to Add Categories and Tags to Pages in WordPress

This one is very straightforward, simply add the below code to your functions file.

function register_additional_taxonomies() {  
	// Add tag metabox to pages
	register_taxonomy_for_object_type('post_tag', 'page');
	
	// Add category metabox to pages
	register_taxonomy_for_object_type('category', 'page');  
}
 // Add to the admin_init hook
add_action( 'init', 'register_additional_taxonomies' );

Go to a page in your WordPress admin area and you should now see the ‘Categories’ and ‘Tags’ metaboxes when editing your page (same as you do on your posts). If not, check that categories and tags are checked in the screen options (you might just need to tick the appropriate screen elements for them to display in your editing panel, as this is customisable to the user and may be unchecked).