The code in the link does work as it should - just not as you want it to. For your purposes, you could use something based on:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim Rng As Range
Set Rng = ActiveDocument.GoTo(What:=wdGoToPage, Name:=3)
Set Rng = Rng.GoTo(What:=wdGoToBookmark, Name:="\page")
With Rng
With .Duplicate
With .Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = "in"
.Replacement.Text = ""
.Forward = True
.Wrap = wdFindStop
.Format = False
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
.Execute
End With
Do While .Find.Found = True
If .InRange(Rng) = True Then
.Text = "on"
.Collapse wdCollapseEnd
.Find.Execute
Else: Exit Do
End If
Loop
End With
End With
Application.ScreenUpdating = False
End Sub
or:
Code:
Sub Demo()
Application.ScreenUpdating = True
Dim Rng As Range
Set Rng = ActiveDocument.GoTo(What:=wdGoToPage, Name:=3)
Set Rng = Rng.GoTo(What:=wdGoToBookmark, Name:="\page")
With Rng.Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = "in"
.Replacement.Text = "on"
.Forward = True
.Wrap = wdFindStop
.Format = False
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
.Execute Replace:=wdReplaceAll
End With
Application.ScreenUpdating = True
End Sub