Sub testaddshape()
  Dim myshape As Shape
    
  Set myshape = ActiveDocument.Shapes.AddPicture(FileName:="c:\test\overlay.png", _
     LinkToFile:=False, _
     SaveWithDocument:=True, _
     Left:=0, _
     Top:=0, _
     Width:=ActiveDocument.Sections(1).PageSetup.PageWidth, _
     Height:=ActiveDocument.Sections(1).PageSetup.PageHeight)
  
     With myshape
      .ZOrder msoSendBehindText
      .WrapFormat.Type = wdWrapBehind
      .LockAnchor = True
      .RelativeHorizontalPosition = wdRelativeHorizontalPositionPage
      .RelativeVerticalPosition = wdRelativeVerticalPositionPage
      .Left = 0
      .Top = 0
     End With
     
End Sub