Even though you have added your preferred PDF viewer in the Kiosk policy, it has not been set as the default viewer for PDF files. Google Docs/Drive app is your current default viewer. So, whenever you try to open a PDF file, Google Drive/Docs attempts to launch itself and since it has not been added in the Kiosk policy, you get the blocked package error.
So, here’s what you do. On the device,
Exit Kiosk mode and open Settings > Apps
Scroll down to Drive (Google Drive app) and tap open the app settings
Select Open by default and tap on Clear Defaults
You can now enable Kiosk mode again. When you open a PDF file again, you will no longer receive the package blocked error, instead, you’ll be asked to select an app to open the file. Choose your preferred PDF viewer and tap the Always use confirmation to set it as the new default viewer. You should now be able to view PDF files while in Kiosk mode.
Thanks and regards
Hexnode Support Team
+1-866-498-9407 (US Toll Free)
+44-(800)-3689920(UK Toll Free)
+61-1800165939 (Australia Toll Free)
Hexnode | Mitsogo Inc.