iBooks app, corrupted PDF

I was using the Books app to study from a PDF file on my iPad, that I had been studying on for months, taking notes, highlighting and everything. After the last update to iPadOS 17.4.1, it seemed to me that some note-taking features like for example the “hold to straighten” for the lines, had been removed from the books app, which I don’t understand why. Anyways I kept using the app, as I had this pdf file full of notes, but today while studying from it, the app crashed and I can no longer access the PDF as it says “unable to open _name of the file_” when I click on it, so it seems that the PDF is now corrupted. Is there a way of restoring it by also restoring the notes I had on it? Or is this not possible since the notes are not directly saved on the PDF? Could I access the notes somehow and import them to a new PDF? This is just unacceptable… hours and hours of work for nothing…