If you don't want to retain the original doc file then
Code:
ActiveDocument.Convert
ActiveDocument.Save
If you want to keep the doc file
Code:
Dim oDoc As Document
Dim sName As String
Set oDoc = ActiveDocument
sName = ActiveDocument.FullName
If oDoc.HasVBProject = True Then
sName = Left(sName, InStrRev(sName, Chr(46))) & "docm"
oDoc.SaveAs FileName:=sName, _
FileFormat:=wdFormatXMLDocumentMacroEnabled
Else
sName = Left(sName, InStrRev(sName, Chr(46))) & "docx"
oDoc.SaveAs FileName:=sName, _
FileFormat:=wdFormatXMLDocument
End If
Set oDoc = Nothing
You might find
Document Batch Processes useful