The system has a page for achievements that you can print off or save. They are kept in the User Dashboard. If you click the Menu button (three-bar button on the upper-right side of the page.) your menu will open.
Click the link next to the blue star labelled "User Dashboard".
Scrolling down a bit you'll see a section with a heading named "Achievements". The first tab labelled "In Progress" displays the Achievement that you can earn but haven't earned quite yet.
Clicking on the "Earned" tab will display the Achievements that you have already earned and can therefore print off right now.