Hi,
I found this diagram on a website somewhere. It shows you what can and can't be done, depending on user and creator versions. I have had this so long that I have no idea where it originated, so apologies to the person I borrowed it from!.
This was for ES2 - you basically have to have the Reader Extensions software for everything in Option 4 (including letting the user attach files). This is a server side application, which doesn't come as standard with ES2. It had to be purchased separately and was quite expensive.
![livecycle_acrobat_versions_options.gif livecycle_acrobat_versions_options.gif](/t5/image/serverpage/image-id/4422i8D97C661DB98883D/image-size/large?v=v2&px=999)
For ES4, there are details about the Reader Extensions on this page:
Modules | Adobe LiveCycle Enterprise Suite 4
No idea of the cost of this one though.
Good Luck