The Docs audit log allows administrators to see when users viewed or edited a document. These logs are available in the control panel under the Reports tab. Logging is disabled by default. It must be enabled in the Drive and Docs settings.
Note that changes made by APIs or views/edits to publicly accessible documents (which do not require authentication) are not logged.
Google Apps, Google Apps for Business, Government and Education
For more information
How to use, access and export the log check this link: https://support.google.com/a/bin/answer.py?hl=en&answer=2789151&topic=2789148&ctx=topic