File sharing

I have a ton of PDF files that I need to have access to, but not store permanently on my iPhone and iPad. I would like to bring up a file on the phone, use it and then delete it off the device without deleting it from where it is being stored.

Does an app exist that will do this? I've looked, but the ones I've tried delete the PDFs from the cloud as well as the device.

Any help would be appreciated. I'm getting desperate.

I'm not clear on why you can't just store the files on, say, Dropbox and open them directly from the app.

When I undelete a file in Dropbox on my Mac (after deleting it on my device) it shows back up on my iPhone and iPad. If I leave it deleted, I can't access it on my phone when I need it again. Unless I'm doing something wrong. That is highly probable.

Unless you mark the file as a favourite the file is not stored on your phone using the Dropbox app. It's just downloaded for viewing then discarded when you close the app. No need to delete the file