Hi Philip,

You can refer these two apps from Cybrosys and create your own app for project attachments.

website_event_attachements

website_product_attachments

I would recommend creating a Project with a Task called "Documents" that contains the URL of a shared Document Workspace.

1. Create the Project

2. In the Documents App, find the Workspace that was automatically created and click SHARE to get the URL and manage security:

3. Add the URL to a new Task you create in the Project called "Documents"

4. Share the Project on the Portal:

Your Portal Users will then see something like this when the click the URL:

If you add chatter to project form view, and put attachments as project's notes, customer would see attachments in portal and even recieve it via email.