Ghostscript must be installed to run the backend with PDF support.
Before running the backend, set GHOSTSCRIPT_PATH to be the path to the ghostscript executable. E.g., /home/keane/gs.
If you are serving the frontend locally, you will need to change the backend's Access-Control-Allow-Origin header to be localhost or 127.0.0.1.
The frontend uses BACKEND_URL for its API requests. If that environment variable is not set, localhost:5000 is used by default.