How can I export all of the highlights, notes, etc I've made on some pages?
Edu Pro users can export annotations that are in Projects by selecting the sources in their project library and selecting the "Create Summary" option in the dropdown menu off of the Create Bibliography. This will provide you the text of all your annotations, as well as the content of any notes you wrote on the source.
If you don't have a project yet, Click on the Projects link at the top of your library and click the Create Project button. Once created, navigate back to My Library and select the sources and click on "More"->"Move/Copy". Choose the Project library you just create and click Move. Then head back to the Project Library and follow the instructions above.