I'm looking for a solution for the same thing. I have a pdf form with fields bound to an xml file, but Acrobat will only import the data manually (Forms / Manage Form Data / Import Data) and Reader doesn't work at all.
Tech Support says that when in Livecycle, you're working in an xml environment, so the 'Preview PDF' works. Acrobat and Reader aren't xml environments, so they won't display the data.
To be able to merge data onto a form you can use a server based piece of software called LiveCycle Forms.