First, click the Download button in the top right of the menu bar.
The Export Options (either to Google Drive or locally):
Original - No Annotation: This option will allow you to download the raw PDF file, perfect for if you are opening the document from the web and wish to save it locally.
With Annotations (PDF File): This will export your document with the annotations you have made.
Annotations Only (Text File): This will create a text document with a summary of all annotations and comments made, including their location in the document and their type.