I think for developer who needs to make serious changes on this issue, should considered removing the dependency on Adobe reader.
There are heaps of PDF reader that can do the jobs, however if you need the javascript interaction within a PDF document, i'll bluntly put it, "You're STUFF" (well pretty much the tone from the support here). Because your client program will not be able to initiate the class on acroPDF.pdf in 32bit mode.
I'm trying a quick fix and see if i can initiate the class during runtime in VB6, if that doesn't work, i may have to write my own PDF reader based on some open source from muPDF, SumatraPDF etc. With SumatraPDF, they have no intentions of moving to 64bits and it's compatible with Windows. Maybe something for developer to think about. Of course you need to learn C/C++.
Alternatively you can redeveloped your application all together.
Clearly the support here have no idea that IBM 360 mainframe are still running in today's so call fast pace software world, the same with the 20million VB6 developers.