The Word Document
You can create the Word document programmatically, but far simpler is to create an initial Word document in Word itself, populating it with boilerplate language. When your program is running you will insert the patient-specific (or visit-specific) data to generate the personalized letter. For this example, I've created Patient Letter.doc which I am storing in the C:\Temp directory (shown in Figure 3).
Note to those who need reminding that coffee is hot: I am not a doctor, these are not real medications, and this article is not intended to provide medical advice. 
Figure 3. Boilerplate language
The bookmarks are shown as vertical lines (indicated by the red arrows in Figure 3). While in Word, click on the Insert menu item and then on Bookmarks. You will be asked to name the new bookmark, as shown in Figure 4.
Figure 4. Inserting a bookmark