(Not an official reply)
1. There is fee based support for development, not sure of the details.
2. Be sure you already have the Acrobat 8 SDK if you plan this route as it is discontinued and not available (Adobe withdrew it and never gave anyone else rights to distribute)
3. Licensing may be complex, as Acrobat is essentially for personal use. If the process is fully automated this is the sort of thing that people have identified as a problem in the past. If the plug-in is run by a click, to make files, which are then taken away with a different manual process, may be OK.
4. Not clear what API there is to automation at all, except for something called (from memory) DigSigCompareDocumens.
5. No API to batch processing. But a plug-in can process batches.