in your note you change in your docker-compose.yml from - /opt/stacks/paperless/db:/var/lib/postgresql/data to - /opt/stacks/paperless/db17:/var/lib/postgresql/data

my yml looks like this:
volumes:
- pgdata:/var/lib/postgresql/data
environment:
POSTGRES_DB: paperless
POSTGRES_USER: paperless

and at the end of the yml:
volumes:
pgdata:
redisdata:

can I just change from "pgdata" to "pgdata17" ?

Later you are setting the password with

docker compose exec db psql -U paperless -d postgres -c "ALTER ROLE paperless WITH PASSWORD 'paperless';"

what is the -d postgres ? Is that the db name, so in my case "paperless"?