Is it possible to not use Document Server to store the documents?

Can Document Server be used only to view/edit files stored in an already existing system? If so, are there any examples?

Hello @joshjava
Document server doesn’t contain any users files or data. The common scenario of DS usage is integration with some storage\app.
If you are independent integrator, please take a look at these titles:
ONLYOFFICE Api Documentation - How It Works - different scenarios
ONLYOFFICE Api Documentation - Language-specific examples - ready-to-test examples of integration

If you are looking for ready-to-go integration, please take a look at pre-made connectors: Download official ONLYOFFICE connectors | ONLYOFFICE

If I misunderstood your request, please clarify it.