You can view the activity log of a document to see who has done what and when on a document.
1. Open the document.
2. Open the More actions menu and select Document history.
3. The history of the document is displayed in a new tab. You can toggle between the document properties and the history by selecting the required tab.
4. To access older events in the document history, press Show next events at the bottom of the page. All the events associated with the document and its attachments will be listed in the document history.
To see the modifications to attachments, use the version control feature.
Learn more: Manage document versions in an AODocs library.