Yes, once you have checked in, you can still change your travel documents, provided that none of the flights in your booking is within 4 hours of departure. You can update your documents via the website by following these steps:
Log in to your myRyanair account.
Go to Manage My Bookings.
Select Manage this booking for the booking you wish to update.
Under Passenger Details, select Change Travel Documents.
Choose the passenger whose documents you want to update, make the necessary changes, and save them.
.