Sub Maketxtboxhidden()
'  With a macro it is possible to cycle through all text boxes
'  and make the content hidden.
'
Dim shp
For Each shp In ActiveDocument.Shapes
  If shp.TextFrame.HasText Then 
   ' if the shape is a textbox
   shp.TextFrame.TextRange.Font.Hidden = True
  End If
Next
End Sub


Sub Maketxtboxunhidden()
'  With a macro it is possible to cycle through all text boxes
'  and make the content unhidden.
'
Dim shp
For Each shp In ActiveDocument.Shapes
  If shp.TextFrame.HasText Then 
    ' if the shape is a textbox
    shp.TextFrame.TextRange.Font.Hidden = False
  End If
Next
End Sub