I have many PDF and epub books that I have manually added to my Books library. However, when I try to open them, many times they have to be downloaded from iCloud because somehow they were uploaded behind the scenes and deleted from the local drive. How can I prevent this from happening? I haven't found anything in the settings allowing me to do this. I want to keep syncing on because I want the books to also show in my mobile devices, but I don't want the books to be removed from the local drive when they're uploaded to iCloud. I want to always be able to access them offline on my laptop. Is this possible?