best practices for moving content between documents

I'm actually here to solicit information about moving content between documents in an established documentation set. 

I think the story is pretty common: you've been documenting a product for a number of years - feature XYZ initially had 20 pages of documentation. This grew to 50, then to 100, then added other supporting documents like reference tables. It's time to give this feature its own document.

So how do you handle it? Are there any pitfalls involved with simply moving the feature and describing the move in document release notes? Should you put a pointer where the text used to be: "XYZ has been moved to Document #09828202, section 2."

Honestly, I don't get much user feedback, except when something is explicitly wrong or incomplete. So as much as I can anticipate confusion, I probably won't get any desperate help requests, but I'd like to do this the right way.  How do you handle this situation?