Word 2013 showing two pages side by side

To view a single page at a time, select the View tab on the ribbon and click One Page.

The issue is with the zoom size. I solved this by setting the default zoom to 120%, and then only a single page is displayed by default.

To set it to 120% by default, you'd need to add a macro:

1. When viewing any Word document, press Alt+F11 to activate the Visual Basic Editor
2. Click on Normal on the left hand side
3. Select Insert -> Module

4. Copy the following code into the module:

   Sub AutoNew()
       With ActiveWindow.View
          .Type = wdPrintView
          .Zoom = 120
       End With
   End Sub
   
   Sub AutoOpen()
       With ActiveWindow.View
           .Type = wdPrintView
           .Zoom = 120
      End With
   End Sub
   

This will set the zoom percentage to 120% for every new document and for every document that you open. You can change 120 to another percentage if you prefer.