You will need the basic paging server for this. Starting 9.1 the basic paging server is included with CUCM.
Refer: https://supportforums.cisco.com/discussion/11699686/paging-and-notification-features-included-cucm-91
Ref: http://www.cisco.com/c/en/us/support/docs/unified-communications/paging-server/117059-configure-informacast-00.html
Note the limit for free version is 50 phones.
-Terry
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