Is there a way for a user to view and download all their posts? If it's not built-in, is there any paid plugin that has been written for this? Or is there a way even for a Moderator or Admin to do this for them?

There's the "View Activity" button on the user's profile, but I don't know how far back it goes.

There is no download option for content, just for personal data (in the ACP). 

Thanks, I wanted to make sure I wasn't missing something obvious!