I've been going out of my mind trying to find the information I'm looking for, so hopefully someone can help me out. I see that when a user converts a Lead to an Account/Opportunity, the attachments (Notes & Attachments section) from the Lead transfer over to the Account. I need to be able to do the same between Opportunities and a custom object I built.

I'm familiar with passing values through a URL - I am using this function to pass data into the custom object at creation presently - but I don't see how to pass attachments. Can somone please give me some idea of how to do it?

If it's easier, it would be even better if I could set up attachment upload areas within the custom object that would intersperse the attachments in various areas around the custom object layout. (The client doesn't really like having to batch everything in one area for this giant layout.) I'm attaching an image so you can see what I have in mind.