Add the Download folder to Kiosk mode device control

Hello, We are using Zebra ET51 GMS tablets on Android 8.1.  Running Soti Mobicontrol Cloud. Our team will be downloading PDFs and JPGs from a web portal through Soti Surf. They need to be able to open these downloaded documents, modify and then upload back to the website portal. These devices are configured for Kiosk Mode using the device control options. I am able to add "Downloads" (com.android.providers.downloads.ui) or Download Manager (com.android.providers.downloads) to the Kiosk screen, but am unable to open any of those 2 directories.  I've tried Launch://, File://, Folder://, Activity://, and still no luck. Is this something that is possible? Is this the best way to go about it also? We don't want them having access to the root directories or any other folders besides Downloads. Our Soti Mobicontrol is cloud hosted, so I am not sure if Soti Hub or Content Library would work since these devices don't authenticate to our environment.  Any ideas on how I can get this to work? Thank you!