It sounds like you're encountering a couple of issues while developing your copilot. Let's address them one by one.
Firstly, regarding the error "The website cannot include a query string" when uploading knowledge through your OneDrive folder, this issue might be related to the way OneDrive API handles query strings. In OneDrive API requests, children's collections of referenced items are not automatically expanded to reduce network traffic and response time. You can use the expand query string parameter to instruct the OneDrive API to expand a children collection and include those results
Secondly, about the number of PDFs you can upload, there isn't a specific limit on the number of PDFs you can upload to OneDrive. However, there are file size limits to consider. For example, the maximum file size for uploads is typically 100 GB per file
Lastly, regarding whether copilot can give you answers through the images in the PDFs, copilot can indeed process and provide answers based on the content of images within PDFs. This capability is part of the broader functionality of copilot to handle various types of content, including text and images