Hi @kathynguy - apologies for the inconvenience. Does it still happen? Do you get the same error no matter any PDF or image you try to add?
If this is still happening, can you open that model in the Power Apps portal. When you open a model, the page address URL will be something like https://make.powerapps.com/environment/a12646b1-2c67-4a20-aefb-c2a33041390f/aibuilder/models/63a8449f-93f5-4ae7-94a8-48055bc570ee
Could you share with us the last part of the URL? This is the model ID that we can use to investigate what might be the issue.