Can we attach files to the Planned Activities in an Opportunity?

Hi experts,

Is that possible to attach files to the Planned Activities in an opportunity?

When I change the Sales Stage of an Opportunity, Activities are are created under Planned Activities assignment block. How can I attach files to those Activities automatically so that when I go into those Activities, i should be able to see the attachment in their Attachments assignment block.

Any help is appreciated.

Thanks,

Abhinav