If you want to read the rtf code just try to use:
Word.Application wordApp = new Word.Application();
Word.Document currentDoc = wordApp.Documents.Open("file.docx");
currentDoc.SaveAs("file.rtf", Word.WdSaveFormat.wdFormatRTF);
And then open it like a normal text file:
string rtf = File.ReadAllText("file.rtf");
Using your method doesn't work because you're accessing Text property, so Word gives you only plain text.
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