How to get the last page viewed by the user of a pdf document opened on my site using pdf.js?

Question

PDF

Hello!
In my Java EE project, I use pdf.js for users to view pdf documents. So the question is: how to remember the page that the user viewed before leaving the site? This is necessary so that the next time the same document is opened, the user starts from the last page read.
I think that this can be done by opening a document reading window inside a jsf page and slightly modifying the js code responsible for displaying the current page. Well, for example, assign prorotype.getPage() to a hidden element. However, I don’t know how to save this value in the database further. I don’t have enough experience :( Sorry if I didn’t explain clearly.
I would be glad for examples, explanations, instructions.