There are a few different ways that you can keep track of changes in a workspace, depending on the type and granularity of information that you prefer. There are also some specific ways of following up on document changes.
In the detail view of activities, milestones and cards, you can find the complete history by selecting the Show history option in the comments section.
Email and web notifications
You automatically follow activities, milestones, or cards that you have created or commented on. This means that you will receive notifications (both email and in the service) when someone else add a comment.
Daily and weekly reports
Information on workspace updates are included in the daily and weekly reports that you can choose if you want to receive or not. The daily report gives a view of what has happened the last 24 hours in the workspace. The weekly report gives an update on the overall work progress, including warnings for overdue milestones and activities.