Friend Sub PageSetupDialogHidden()
    Dim dlg As Word.Dialog = Application.Dialogs.Item(Word.WdWordDialog.wdDialogFilePageSetup)

    ' Set the properties of the dialog box.
    ' ControlChars.Quote() is used to represent the symbol for inches.
    With dlg
        .PageWidth = 3.3 & ControlChars.Quote
        .PageHeight = 6 & ControlChars.Quote
        .TopMargin = 0.71 & ControlChars.Quote
        .BottomMargin = 0.81 & ControlChars.Quote
        .LeftMargin = 0.66 & ControlChars.Quote
        .RightMargin = 0.66 & ControlChars.Quote
        .HeaderDistance = 0.28 & ControlChars.Quote
        .Orientation = Word.WdOrientation.wdOrientPortrait
        .DifferentFirstPage = False
        .FirstPage = 0
        .OtherPages = 0

        ' Apply these settings only to the current selection with this line of code:
        .ApplyPropsTo = 3

        ' Apply the settings.
        .Execute()
    End With
End Sub

private void PageSetupDialogHidden() 
{ 
    Word.Dialog dlg = Application.Dialogs[Word.WdWordDialog.wdDialogFilePageSetup];

    invokeHelper(dlg,"PageWidth","3.3\"");
    invokeHelper(dlg,"PageHeight","6\"");
    invokeHelper(dlg,"TopMargin","0.71\"");
    invokeHelper(dlg,"BottomMargin","0.81\"");
    invokeHelper(dlg,"LeftMargin","0.66\"");
    invokeHelper(dlg,"RightMargin","0.66\"");
    invokeHelper(dlg,"HeaderDistance","0.28\"");
    invokeHelper(dlg,"Orientation","0");
    invokeHelper(dlg,"DifferentFirstPage","0");
    invokeHelper(dlg,"FirstPage","0");
    invokeHelper(dlg,"OtherPages","0");

    // Apply these settings only to the current selection with this line of code:
    invokeHelper(dlg,"ApplyPropsTo","3"); 

    // Apply the settings.
    dlg.Execute(); 
}

private static void invokeHelper(Word.Dialog dlg, string member, string value)
{
    System.Type dlgType = typeof(Word.Dialog);

    // Set the appropriate property of the dialog box.
    dlgType.InvokeMember(member,
        System.Reflection.BindingFlags.SetProperty |
            System.Reflection.BindingFlags.Public |
            System.Reflection.BindingFlags.Instance,
        null, dlg, new object[] {value},
        System.Globalization.CultureInfo.InvariantCulture);
}