Google Docs that have been published to the web can be annotated in the published view. If you plan to invite others to annotate the Google Doc, be sure to share the published URL (which will end in /pub) rather than the sharing URL. For Hypothesis LMS app users, the guidance is the same; make sure to build your assignment using the published URL only. See this discussion on the difference between publishing and sharing Google Docs if you have questions.
Please note that Google may take a short time between edits on the editing page and the edits showing up on the published page.