Unable to 'open' PDFs in iBooks

Advice needed.

When opening documents my iPad used to give me the option of 'open in iBooks' or in safari. Now it only lets me open in notability. I have not changed any settings so I can only assume this has happened since an update. I do not want to use notability for opening PDFs because I can't be doing with the hassle of converting it and then having a dropbox account.

Does anyone know how to change back so I can use iBooks again?