As an addition to what Lancelot said, I can mention that you can make a template document that contains merge fields and protected regions using Word or our RadRichTextBox and its UI. Afterwards, you can import the template document to our control. The unprotected text will be editable by your users.
In order to fulfill your scenario, you should read the data from Share Point, create objects having the necessary properties and set the collection of these objects as an ItemsSource to the MailMergeDataSource of the document. Finally export the document via docx format provider.
Hope this demo
is close enough to your case and you can manage to test if our controls fit your development scenario. MailMerge is described in this article
All the best,
the Telerik team