In this user guide: Files in Rich Text & Documents it states the max file size is 500mb, and there is no reference to file sizes anywhere else in the guide. When testing, I found it to actually be 1gb.
Side note: when testing this, i noticed that when uploading anything above 1gb, it would throw the error immediately, but when uploading exactly 1gb (unlikely event), it takes a long time to load, and then throws an unclear, undescriptive error.