@siloo10 I second that Idea.
I just googled for it and found this thread.
I am not joining the discusion of PDF-reader being Chromium-based or not, the expresion of the Idea remains the same.
I found my self reading the same PDF (reports, instructions, manuals, government docs, etc.) on the same cite referenced by another ones, and if I download every single one of them to disk and annotate them, then I wont even remember that it is there as it doesn't keeps an URL association nor is linked by a document.
I believe this suggested annotations feature should somehow be stored as cookies, or anything userspace-related, instead of stored into the file itself, appliable to any static content, and synced with user personal-data.
It would improve the internet-reading experience a lot.