The documentation that is supported in SQL Doc is the MS_Description extended property. If you use SQL Compare, you can synch an object in one database with an object in another. The extended property is treated as part of each object in SQL Compare and therefore would be copied across with a synchronization.
Please give this a go and let me know if this solves your problem. If you are unclear about how this works, please respond to this thread or send me a private message.
Red Gate Software