Application.Documents("NewDocument.doc").Close(Word.WdSaveOptions.wdDoNotSaveChanges)
object fileName = "NewDocument.doc";
object doNotSaveChanges = Word.WdSaveOptions.wdDoNotSaveChanges;
Word.DocumentClass doc = Application.Documents.get_Item(ref fileName) as Word.DocumentClass;
doc.Close(ref doNotSaveChanges, ref missing, ref missing);