i need to find backup size of each user, is there any report that tells the data size of each user that is being backed up?
You shoud be able to find the size of the backed up data by lookin at the job log.
For options available for the reports, refer to : http://www.symantec.com/docs/HOWTO24000
There is no such report in the DLO. However, looking at the History tab in the DLO console you should find the Backup done on the NUDF and LUDF for the user.