Hop this help:
from http://service.sap.com/sap/support/notes/1612499
Symptom
What are the minimum rights required to be able to send a report object to another user's inbox on BI Launch Pad?
Resolution
- On the report object that you want to send, the user sending the report object needs the following rights:
- Copy objects to another folder
- Schedule to destinations
- View objects
- On the user account that you want to send to, the user sending the report object needs the following rights:
- View objects
- On the Inbox of the user you want to send to, the user sending the report object needs the following rights:
- Add objects to the folder
- Copy objects to another folder
- On the Temporary storage, the user sending the report object needs the following rights:
- Add objects to the folder
Also, to limit the number of users, have a look at http://service.sap.com/sap/support/notes/1763036