Question:

How can Chatter be enabled for certain profiles in Salesforce?

Answer:

Salesforce allows Chatter to be turned on or off on a per-profile basis. This requires the Chatter by Profile feature is enabled in the ORG.

1. Open a ticket with Veeva Support requesting the Chatter by Profile feature to be enabled in the ORG. Veeva sends the request to Salesforce. 
2. After this feature is enabled, the Enable Chatter option appears under the Administrative Settings section of the Profile.
3. After Enabling Chatter for the Profile, consult the article in the Related Documentation for additional properties of this feature.

Related Documentation:

Salesforce Help Documentation: Control Chatter Access Through User Profiles

Thank you