To navigate the Stats Pack PDF file in your web browser, use the list of bookmarks displayed at the left of your screen.
If you save the Stats Pack PDF file on your computer, go to Menu>View>Show/Hide>Side Panels>Bookmarks. You can also click on the magnifying glass/search symbol from the upper right corner of your page and type the name of the city/region you're interested in.
For example, to find information about London East, go to "EAST Residential". Information about London North can be found under "NORTH Residential", and London South data is under "SOUTH Residential".