Agentforce for Service Superbadge Unit
I managed to do it, I believe it is some antivirus security block or some Windows configuration, my suggestion is to try it on another computer.
It is not something related to the org.
Click on Gear icon -> Select Data Cloud Setup -> Then in Quick find type
Salesforce CRM -> Now there please check is there any active Connection
when tried to upload the PDF from another system it worked. Seems some access issue.