Since you cannot configure a function to be triggered by subdirectories. It's only possible to listen to the entire bucket. If you have a trigger based on Bucket, the recommendation is to create a new, separate bucket so that you are not triggered every time a file changes in the Bucket.
Create a new bucket
Update your Functions environment config with new bucket name
Call the functions.config() to get the specified bucket name
You can do environments for Functions:
$ firebase -P dev functions:config:set storage.bucket="dev-digital-paper-edit"
> ✔ Functions config updated.
$ firebase -P dev functions:config:get
$ firebase -P prod functions:config:get
And then subsequently in a Function you'd use the config like so:
const functions =require("firebase-functions");
const BucketFunctions = functions.storage.object(
A big caveat here - you don't have a document anywhere in your repo that tells you what this is. You need to be logged in into firebase and run the above