The Enhanced PDF viewer has several annotation features available!
The first are highlights, which now come in 4 different colors! To highlight, just select the desired text and a menu should pop up. Choose the appropriate color and your text will immediately be highlighted. To delete unwanted annotations/highlights, select an existing annotation and choose the delete option.
Following the same procedure as explained above, you can also add notes. All of these notes and highlights can be viewed from the left-side menu by selecting the "Notes" tab.