PDFs annotations

I am interested to know if you use some app to annotate PDFs. The problem is: how do you take out a file from Scrivener, annotate, and then reinsert it in the project? Because I think that there is no way to annotate a pdf from within the iOS app.
Any advise would be appreciated.
Have a wonderful day.

The only way to do this would be to export the PDF file to another app, annotate it, and then re-import it. The problem is that, unlike macOS, the iOS file system is entirely closed off and private to each app. That is, each app has its own section of the file system and cannot access files from the file system of another app without copying them. So there’s no way of passing a PDF inside a Scrivener project for editing in another app on iOS.

All the best,