You might face issues while adding the PDF files from Google Drive or any Other cloud service. This is because there is a bug in the Files app because of which it does not download the selected PDF file from Google Drive automatically.
To resolve the issue, the only thing that you have to do is to Open the “Files” app separately and tap on the PDF file that you wish to use with our app. This will make the application download the file in Files app.
After this, open the application and add the file using Files application. This will resolve the issue.
Please see the below video for assistance :