This a useful tip from Lee Miller, HOK Firmwide Revit CAD manager. The question is, "How do I merge two workset projects together?"
Here's what to to; the key to this process, is preparation.
Prepare the models
First make backups of all your work.
Choose the smaller, least complex of the two models, and purge unused.
Get the model as lean as possible.
Determine what drafting elements will need to be preserved
The Binding process
In the model which you will bind your project into, create a new temporary workset. This will be the workset that the bound elements will be dump into.
A message will the appear warning you about binding a linked file. Just choose the remove link button.
It may take some time for Revit to complete this exercise! Depending on the size of your project.
Once the link has been bound, this bound link will be a group. You can then choose to ungroup and the start to transition objects to previously created New worksets.
Finally, recreate views, import sheets, etc as required.