Click on the "Toggle Sidebar" for an overview of the PDF. The sidebar contains 3 buttons - "Show Thumbnails", "Show Annotations", and "Show Document Outline".
In the middle of the toolbar are 4 tools for editing the PDF - "Highlight Text", "Add Note", "Select Area", and "Pick a Color".
The main panel shows the PDF.
Find more tools on the right of the toolbar, such as "Find in Document", and show item information.
