Sets or returns a Document.Gutter object representing the gutter position in this document when it is opened in Word. If you have set up your document with facing pages or two pages per sheet (by using Mirror margins, Book fold, or 2 pages per sheet), then this option is not available. Possible values: Side, Top.

 public Gutter GutterPosition{ get; set; }
Public Property GutterPosition() As Gutter

The default value for a new Document is Document.Gutter.Side.

MS Word equivalent: File menu > Page Setup... > Margins tab > Margins section > Gutter position:

          //--- Return GutterPosition
          Document.Gutter oGutterPosition = oDocument.GutterPosition;

          //--- Set GutterPosition
          oDocument.GutterPosition = Document.Gutter.Top;

          '--- Return GutterPosition
          Dim oGutterPosition As Document.Gutter = oDocument.GutterPosition

          '--- Set GutterPosition
          oDocument.GutterPosition = Gutter.Top