I can’t really find any info on how to do this, or is this still important in 2023? I use a GrapheneOS device.
If you factory reset your phones, the files are not recoverable. If you delete a user profile, the data in that user profile is no longer recoverable.
Most android phones have encrypted storage , so if you factory reset the phone technically it should change the encryption key on reset , thus making any recovery softwares useless too.
If you don’t want to reset the phone , there may not be a full proof method but still you could try a few things like storing documents only in the internal file storage of an app , which makes the storage inaccessible by any externel app.