How to add a page to a document in Books app

Hi I'm currently a college student and use the Apple app "Books" nearly everyday. I love that I can download slides from class/worksheets/practice exams and zoom in/annotate all over them. However the one thing that is frustrating to me is that I can't add a blank page into the pdf. Does anyone know if this is possible? I know you can do it on Pages but Pages wont allow me to just work directly from the slide pdf, I would have to actually create the file itself every time which is not gonna happen lol! Anyways... wondering if this is even possible and if it is... how??

Also I would like to clarify I have an ipad air 5th gen and ipados 17.3.1 if that matters

Thanks!