The trial version is exactly the same as the registered version except it has not be registered and access will expire 30 days after instillation. The subscription version requires a monthly login to the owners adobe account.
and access will expire 30 days after instillation.
I believe it's 7 days now...
In fact, the trial period is now only 7 days!
You are probably running out of virtual memory address space in Acrobat for this much content for the export process.
Why not try doing the export in parts?
Make two copies of the PDF file. Open the first PDF file, delete the 2nd half of the content, and export to Word. Then open the second PDF file, delete the first half of the content, and export to Word. Then recombine the two Word files within Word.
The only big got'cha might be that Word isn't particularly great at handling long, complex documents. For that large a document, you might need to run the 64-bit version of Office (assuming of course that you are running the 64-bit version of Windows).