Sub CustomWatermark()

    Dim activeDoc As Document
    Dim rngDoc As Range
    Dim shpTextBox As Shape
    Dim lngPages As Long
    Dim i As Long
    Dim strWatermark As String
    
    
    Set activeDoc = ActiveDocument
    
    lngPages = activeDoc.Range.Information(wdNumberOfPagesInDocument)
    
    strWatermark = InputBox("Enter Watermark")
    
    With activeDoc
    
        For i = 1 To lngPages

            Set rngDoc = .GoTo(What:=wdGoToPage, Name:=i)
            rngDoc.Collapse wdCollapseStart
        
            Set shpTextBox = .Shapes.AddTextbox(Orientation:=msoTextOrientationHorizontal, _
                                            Left:=InchesToPoints(1), _
                                            Top:=InchesToPoints(4), _
                                            Width:=InchesToPoints(6), _
                                            Height:=InchesToPoints(2), _
                                            Anchor:=rngDoc)
            With shpTextBox
                .Line.Visible = msoFalse
                .Rotation = -45
                .WrapFormat.Type = wdWrapBehind
                .TextFrame.HorizontalAnchor = msoAnchorCenter
                .TextFrame.VerticalAnchor = msoAnchorMiddle
                                                
                With .TextFrame.TextRange
                    .Font.AllCaps = True
                    .Font.Size = "60"
                    .Font.ColorIndex = wdGray25
                    .ParagraphFormat.Alignment = wdAlignParagraphCenter
                    .Text = strWatermark
                    
                End With
            End With
        Next
    End With
    

End Sub