The behavior is by design. The zoom level at which Word displays a single page, centered in your monitor, depends on the monitor size and resolution. What you can do is run a macro as follows:
Code:
Sub ChangeTheZoomAsDesired()
On Error GoTo errhandler
ActiveWindow.View.Type = 3
With ActiveWindow.View.Zoom
.PageColumns = 1
.Percentage = 120
End With
errhandler:
Exit Sub
End Sub