Audit Trail - track users opening Documents

Hi All

I am building a community in 15.6 that includes the following "audit" requirement:

- Track when users log into the system

- Track which users open a document

When I look through the posted Audit Trial guide, I see lots about create and delete of objects, but nothing about how Users interact with them. Under the "User" Select Object Type in the Audit Trail in eB SMC I find an item called "Logged On", but am not able to make "Tracking Required" and so do not see any Audit entries in the "Audit Details" section of the Person object for my test user.

Any ideas and help would be appreciated.

Thanks, Alistair