Your macro doesn't do what you indicate it is supposed to do. Try the following, which does.
Note that C:\Desktop is not the usual location for the Windows desktop
That would be Environ("USERPROFILE") & "\Desktop\"
Code:
Option Explicit
Public Sub PageAdd()
Dim myFile As String
Dim PathToUse As String
Dim myDoc As Document
Dim rngStory As Word.Range
PathToUse = InputBox("Enter path to the documents:", _
"PageAdd", _
"C:\Temp")
If PathToUse = "" Then Exit Sub
If Right(PathToUse, 1) <> "\" Then PathToUse = PathToUse & "\"
'On Error Resume Next
myFile = Dir$(PathToUse & "*.doc*")
While myFile <> ""
'Open document
Set myDoc = Documents.Open(PathToUse & myFile)
Set rngStory = myDoc.Range
If myDoc.BuiltInDocumentProperties("number of pages") Mod 2 <> 0 Then
With rngStory
.Collapse wdCollapseEnd
.InsertBreak wdSectionBreakNextPage
.End = myDoc.Range.End
.Collapse wdCollapseEnd
.InsertFile FileName:="C:\Desktop\NOTUSED.DOCX", link:=True
With .Sections(1).Headers(wdHeaderFooterPrimary)
.LinkToPrevious = False
.Range.Text = ""
End With
End With
myDoc.Close SaveChanges:=wdSaveChanges
Else
myDoc.Close SaveChanges:=wdDoNotSaveChanges
End If
'Next file in folder
myFile = Dir$()
Wend
End Sub