create a watermark using one of the built-in watermarks in a new blank document. Open the header and select the Word art. Change the text to 'Page left blank' then while it remains selected ALT+F3 and save it as an autotext entry called 'Blank Page'. The following, based on your code, should then create the blank pages and add the autotext across each.
Code:
Sub PageBreakSectionSeparator()
Dim Sect As Section
Dim iSec As Integer
Dim oRng As Range
Dim iValue As Integer
With ActiveDocument
On Error Resume Next
' go through each section (except for the last one)
For iSec = 1 To .Sections.Count - 1
' create a range object at the start of the section
Set oRng = .Sections(iSec).Range
oRng.Collapse wdCollapseStart
' insert a sectionpages field
.Fields.Add Range:=oRng, Type:=wdFieldSectionPages
' divide the sectionpages field by 2
' if it gives a zero as the remainder, then
' you have an even number of pages in the section,
' which is what you want with an odd section page break
If (.Sections(iSec).Range.Fields(1).Result Mod 2) <> 0 Then
' if you have an odd number of pages, then insert
' a page break before the section's section break
Set oRng = .Sections(iSec).Range
With oRng
.Collapse direction:=wdCollapseEnd
.MoveEnd unit:=wdCharacter, Count:=-1
'Ensure the insertion point is at the end of the text
.MoveEndWhile Chr(13) & Chr(32), wdBackward
'Insert a page break
.InsertBreak Type:=wdPageBreak
'Move the insertion point to the blank page
.End = .Sections(iSec).Range.End - 1
.Collapse direction:=wdCollapseEnd
'Insert a building block with the required notification
NormalTemplate.BuildingBlockEntries("BlankPage").Insert _
Where:=oRng
End With
End If
' remove the sectionpages field that was added
.Sections(iSec).Range.Fields(1).Delete
Next iSec
End With
End Sub