Using iCloud to backup local data automatically

Is it possible to use iCloud to backup files that are currently stored locally so that those files appear on other devices? And can this be done automatically with the user having to take explicit action to do periodic backups? I have an existing app in which the user can create local files. If I add iCloud support I do not want the users to have to move all their files to iCloud Drive first. I do not want to disrupt the current usage more than necessary.