Can I send different files to different recipients in the same email? If so, how do I do this?

Yes. In the second step Compose of creating a Certified Email, you can choose to attach the same file(s) for all your recipients by dragging them into the "For All" tab in the Attachments section (Optional).

To send different files to different recipients, you must do so through the "By Recipient" tab in the Attachments section (Optional), by dragging the files into each recipient's respective box. Files sent to a specific recipient will only be visible to them.