You could track user activity through audit logs. Here are steps:
1.Go to Central Administration -> Manage service applications -> Select Secure Store Service application and click the properties from the ribbon -> Enable audit and set the number of days to keep audit logs until be purged.
2.Go to Site settings -> Click the Site collection audit settings -> Configure the audit log settings.
3.Go to Site settings -> Site content types -> Click the content type you want to -> Click the Information management policy setting -> Enable auditing.
4.Go to Site settings -> Site collection features -> Activate Reporting feature.
5.Go to Sites settings -> Click the Audit log reports -> Click content viewing report, you also can click custom reports to custom your content viewing report.
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