Not only you can launch the work-assistant by just asking Cortana, you can search for documents with help of voice command and even open, view and edit them. You can also share to documents to your contacts by just asking work-assistant to do so.
In fact, a Beta app called “Work-assistant” was leaked that belongs to Microsoft’s “internal Beta account”. The description of this Beta app reads “Work-assistant prototype”. So, it seems the Work-assistant is in early stage of developments and may be shipped with future preview builds.
Thanks Haldar for the detailed tip. Cheers!!