Fix "undefined label" warnings caused by missing leading underscore in the label

docs/topics/pages.md

@@ -168,7 +168,7 @@ These are used for structuring fields in the interface.
 The page editor can be customised further. See [Customising the editing interface](/advanced_topics/customisation/page_editing_interface).
 
 ```eval_rst
-.. page_type_business_rules:
+.. _page_type_business_rules:
 ```
 ### Parent page / subpage type rules
 
@@ -184,7 +184,7 @@ By default, any page type can be created under any page type and it is not neces
 Setting `parent_page_types` to an empty list is a good way of preventing a particular page type from being created in the editor interface.
 
 ```eval_rst
-.. page_urls:
+.. _page_urls:
 ```
 ### Page URLs
 
@@ -464,7 +464,7 @@ news_items = NewsItemPage.objects.live().order_by('-publication_date')
 ```
 
 ```eval_rst
-.. custom_page_managers:
+.. _custom_page_managers:
 ```
 ### Custom Page managers
 

docs/topics/permissions.rst

@@ -25,7 +25,7 @@ Whenever a user creates a page through the Wagtail admin, that user is designate
 
 The full set of available permission types is as follows:
 
-* **Add** - grants the ability to create new subpages underneath this page (provided the page model permits this - see :ref:`page_type_business_rules`), and to edit and delete pages owned by the current user. Published pages cannot be deleted unless the user also has 'publish' permission.
+* **Add** - grants the ability to create new subpages underneath this page (provided the page model permits this - see :ref:`Parent page / subpage type rules<page_type_business_rules>`), and to edit and delete pages owned by the current user. Published pages cannot be deleted unless the user also has 'publish' permission.
 * **Edit** - grants the ability to edit and delete this page, and any pages underneath it, regardless of ownership. A user with only 'edit' permission may not create new pages, only edit existing ones. Published pages cannot be deleted unless the user also has 'publish' permission.
 * **Publish** - grants the ability to publish and unpublish this page and/or its children. A user without publish permission cannot directly make changes that are visible to visitors of the website; instead, they must submit their changes for moderation. Publish permission is independent of edit permission; a user with only publish permission will not be able to make any edits of their own.
 * **Bulk delete** - allows a user to delete pages that have descendants, in a single operation. Without this permission, a user has to delete the descendant pages individually before deleting the parent. This is a safeguard against accidental deletion. This permission must be used in conjunction with 'add' / 'edit' permission, as it does not provide any deletion rights of its own; it only provides a 'shortcut' for the permissions the user has already. For example, a user with just 'add' and 'bulk delete' permissions will only be able to bulk-delete if all the affected pages are owned by that user, and are unpublished.