I believe answer get your company to buy you the upgrade...
Problem is, they may respond "spend all your time in the office and it's not a problem".
In the meantime, it turns out that the "fast save" option was always turned off. So, I tried turning it on - no change. I tried turning it off again - no change.
Aaaarrrggghhhhh !
G
(And this was in a session where I'd not run Acrobat reader).