Document notifications settings are available to every user in My notifications menu and can be adjusted at any time.
The project administrators have the following settings available:
Send emails about uploaded and deleted documents.
Notify about documents that I uploaded or deleted myself.
Notify on uploaded data volume reached.

While the guest users (non-administrator user roles) can only receive notifications about new documents:

Notifications about new documents set to "Daily in the morning" or "Daily in the evening" will be sent out at 8 am or 8 pm respectively, according to a user's time zone settings.
Project administrators can specify the frequency of document notifications for their users during the invitation (the default value is Never)

or/and change notifications on newly uploaded documents for users any time later.
Please refer to this article for more details on what is considered a new document addition and when the notifications are sent out to the users.
Here you may find alternative ways to inform your users about specific documents if needed.