Dear Talha,
Good day! Thank you for your detailed information. We are here to assist you.
It sounds like you're encountering an issue with uploading your PDF file in Copilot Studio.
I understand how important it is to get this issue resolved. However, since our community is mainly focus on the Microsoft 365 and Office built-in features and this specific query might require more specialized assistance, I recommend visiting the Microsoft Copilot - Microsoft Q&A. The experts and other users there have a wealth of knowledge and should be able to provide the detailed help you need. The Microsoft Copilot - Microsoft Q&A is a great resource for specialized assistance.
As you know this is beyond my expertise, however I did some online research and found that Files greater than 512 MB aren't supported. Files that contain encrypted content, are password-protected, or contain confidential tags, aren't supported. The maximum number of files that can be included as knowledge in an agent is 500 files. For more information, please check Upload files as a knowledge source - Microsoft Copilot Studio | Microsoft Learn
Please accept my apologies for redirecting you to the related team support, as the moderators in this community have limited resources and permission to verify the backend information and to get the quick and better assistance, we requested for this.
I hope you are staying safe and well! Have a great day and take care! 😊
Sincerely,
Naren | Microsoft Community Moderator