The following should work  - try it on a couple of files in a folder before
committing to a large print run ;)

Sub BatchPrint()
On Error GoTo err_FolderContents
Dim FirstLoop As Boolean
Dim DocList As String
Dim DocDir As String
Dim fDialog As FileDialog
Dim intPages As Integer
Set fDialog = Application.FileDialog(msoFileDialogFolderPicker)

With fDialog
   .Title = "Select Folder containing the documents to be printed and click
OK"
   .AllowMultiSelect = False
   .InitialView = msoFileDialogViewList
   If .Show <> -1 Then
       MsgBox "Cancelled By User"
       Exit Sub
   End If
   PathToUse = fDialog.SelectedItems.Item(1)
   If Right(PathToUse, 1) <> "\" Then PathToUse = PathToUse + "\"
End With

If Documents.Count > 0 Then
   Documents.Close savechanges:=wdPromptToSaveChanges
End If
Application.ScreenUpdating = False
FirstLoop = True
DocList = Dir$(DocDir & "*.doc")

   Do While DocList <> ""
       Documents.Open DocList
       intPages = ActiveDocument.BuiltInDocumentProperties(wdPropertyPages)
       If intPages Mod 2 = 0 Then
           ActiveDocument.PrintOut , PrintZoomColumn:=2, PrintZoomRow:=1
       Else
           ActiveDocument.PrintOut
       End If

       ActiveDocument.Close savechanges:=wdDoNotSaveChanges
       DocList = Dir$()
       FirstLoop = False
  Loop

Application.ScreenUpdating = True
Exit Sub
err_FolderContents:
   MsgBox Err.Description
   Exit Sub
End Sub