I've got Professional version 8 installed. The info below is from the legal notice contained in my install.
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14.13.3 For any unique Extended Document, you may only either (a) Deploy such Extended Document to an unlimited number of unique recipients but shall not extract information from more than five hundred (500) unique instances of such Extended Document or any hardcopy representation of such Extended Document containing filled form fields; or (b) Deploy such Extended Document to no more than five hundred (500) unique recipients without limits on the number of times you may extract information from such Extended Document returned to you filled-in by such Recipients. Notwithstanding anything herein to the contrary, obtaining additional licenses to use Acrobat Professional shall not increase the foregoing limits (that is, the foregoing limits are the aggregate total limits regardless of how many additional licenses to use Acrobat Professional you may have obtained).
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A - (500) INSTANCES - Transactions / UNLIMITED Users
B - (500) USERS - Recipients /UNLIMITED Instances
I've seen other discussions in forums about how they'd enforce it.
I've also wondered about PDF ebooks/products. Say you rights enabled one with some type of form field, for whatever purpose. And you marketed and sold it as a product. If the form wasn't used in any kind of "extracting information" as mentioned above, would it then be legal to "deploy" it to more than 500 people....? It would be an Extended Document, but again, no transactions.
The wording in legal notice to me implies more of a business scenario, web or email based transactions, that type of mind-set.
I'd be interested on someone else's interpretation of the legal stuff.
Thanks
Mike Foster