Thanks for the feedback & apologies for the late reply!

Regarding multiple PDFs, that is def. on the plan as I figure out the standalone desktop version of the app. Right now, running multiple browser tabs side-by-side works ok, but there is one counter-intuitive quirk to keep in mind due to local browser storage: the app stores a single document as the global "most recently opened" PDF - so when you open a fresh tab it will automatically load whichever file was opened last, rather than remembering that specific tab's previous book.

That said, your saved work is completely safe. Annotations, highlights, and bookmarks are strictly tied to each PDF file's unique ID. Just keep in mind that refreshing an individual tab will jump it to whatever book you opened most recently.

Hope that makes sense