Good Day Sutot.
I assume this is related to SC R14.1 and the SC-UI(not the USS-UI?).
For a CA Service Catalog(SC) request, you can set an attachment to be required.
For Notes, this functionality does not exist, ootb.
You might want to add an Idea for this kind of functionality to be implemented in the future?
I am not sure though, but possibly, you can add/write your 'own' java-script-coding into an SC-form. to be attached to the service(option)? Not sure though whether that code would then be executed at 'sc-request-approval' time.
Thanks and kind regards, Louis.