Thanks, I will try this.

These documents part of a process, and later they want to manage it without the workflow and List, like a document archive.

Just a recommendation...I wouldn't create a folder. In SharePoint try to steer away from folders and use a field that is a lookup 'type' or choice field or put them in different document libraries. For example: instead of creating a folder for Mustang, Lexus, BMW, etc create a field that is a lookup to a car type list. Or create a document library for each. That way things don't get lost in folders and users won't duplicate things so easily.

Unfortunately, I couldn't solve it easily. We can use SP web services for this, but it's too complicated for business users whom try to use it as a self-serv tool. (We avoid UDAs for other reasons... but that's a possibility to encapsulate the logic) We plan to develop a custom control for this scenario.

We (with Dániel Baranyi ) already developed a control to upload files from task forms attachment, directly to the list item attachments...