If you want to create a multipage document much like this user manual, the book module is the tool for you. The book module is not enabled by default, but it is available for you to enable through the Functionality menu when logged in as an admin.
The book module has powerful outlining functionality and allows you to create parent/child relationship between pages.
The book module is very similar to the same feature in Drupal 7. If you need additional help, you should be able to make use of the many Drupal 7 resources available.
