The new document viewer will need to be enabled to gain access to all the new features. First go to "Account Settings", click your name at the top right of the homepage and then click account settings.
In account settings window on the lower left side panel you will select a tab that is named "Labs".
You can also follow this link to access Labs: LINK
You will then need to toggle on the new document viewer.
Congratulations you now have access to the new document viewer. Simply open a document in any case and you will be greeted with a short walkthrough to see the newly added features.