Hello Paul Létoquart and welcome to the Microsoft Community!
Based on your feedback that you are experiencing the inability to download files (e.g. PDFs) as input to Copilot for your opilot Pro subscription, I think you deserve a good service and reasonable benefits as a paid subscriber.
I feel that you, as a paid subscriber, deserve a good service and reasonable benefits.
I therefore recommend that you use the telephone support to access the service.
It is not possible to troubleshoot paid projects in the forums.
Most of the issues dealt with in the forums are day-to-day user issues.
Therefore, you can contact the telephone support staff by the following methods
Click on the following URL
Then enter your question and click “Login to Contact Support” below.
A phone support person will then call you to help you resolve the issue.
I hope you find the above information helpful, please let me know if there is any progress and I look forward to hearing from you!
Kirito|Microsoft Community Support Specialist