WordPress.org

Who can view the help documents?

Anyone who can publish posts. So by default, Authors, Editors, Administrators.

Who can edit the help documents?

Anyone who can manage WordPress options. So by default, Administrators.

How do I reorder the documents?

Just like you'd reorder pages. Change the Order setting for the page, in the Attributes meta box. To make something be first, give it a large negative number like -100.

How do I link to another help page from a help page?

Use WordPress' internal linking feature. When launched from a help document, it will only search for other help documents.

How do I change the default help document?

Edit the help document you want to be the default. Find the "WP Help" meta box. Check the checkbox, and save. This will now be the default document