To me it cost me a lot to find it, but after much searching, I've gotten that I appear exactly like the statue on the Apple website.
I used to get two apps that support iCloud Drive. Are Scanner Pro and PDF Expert Readdle both. With the better it works is with PDF Expert as pressing the central icon bar below the app will appear, but is more expensive than Scanner Pro. For Scanner Pro you aparce a button top left where it says iCloud Drive and pressing all folders will appear.
With apps Apple Pages etc, only accesses a full part of iCloud and not drive all your folders.
Maybe there are more apps that allow to do this but I only know these two.
I hope you know useful. Greetings.