Navigate to Case File page.
Collapse all the Taxonomies in the EFC Tab.
Expand only the Taxonomies you would like to transfer.
Click on the Checkmark to select all the displaying documents. (If you only need certain documents, then you can select them individually.)
Once you have selected the documents you would like to transfer, click on the Transfer Case button.
In the Transfer Case pop up window under the Transfer drop down, select Selected Case Files.
After you have selected the Selected Case Files option in the drop down, proceed to transfer the case as any other.
NOTE: If you still need any of the documents you had transferred, then you can retrieve them from the Transferred Documents Recycle Bin.