 <p>It sounds like an encoding issue. You're probably saving down as a different encoding to the original document, and different from what the target application is expecting. Hence the change in file size.</p> <p>It's possible to change the encoding used for the save as described by dbc above:</p> <blockquote> <p>Create an XmlWriterSettings, set XmlWriterSettings.Encoding as appropriate, then create an XmlWriter and pass it to XDocument.Save().</p> </blockquote>