In order to make this feature more accessible, I've created a macro which toggles between Vertical Top and Vertical Center alignment. You can then add a button to your Quick Access Toolbar, so changing the vertical alignment of a page becomes a snap:
Sub V_Align()
'
' Vertical Align on page Macro
'
'
If (ActiveDocument.PageSetup.VerticalAlignment = wdAlignVerticalTop) Then
ActiveDocument.PageSetup.VerticalAlignment = wdAlignVerticalCenter
ElseIf (ActiveDocument.PageSetup.VerticalAlignment = wdAlignVerticalCenter) Then
ActiveDocument.PageSetup.VerticalAlignment = wdAlignVerticalTop
End If
End Sub