What Adobe Reader wants you to do is get access to Adobe Reader Pro (note there is a time-limited free fully-functional trial), open the PDF, go to
File > Save As Other... > Reader Extended PDF > Enable More Tools (includes form fill-in & save)...
(That's a triply-nested menu!)
And then you get a PDF file that looks just the same, but will have all those other options no longer greyed-out when opened in the free Adobe Reader. This includes the entire
Comment & Markup Toolbar * showing up, as well as all the tools that can be enabled on it.
The most striking aspect of this story is that Adobe wants us to jump through hoops after we paid for the Adobe Reader Professional. And it doesn't even tell us that it wants us to buy the Pro version to enable these tools. What, "enable document rights" is supposed to be self-explanatory? It's a complete usability mess. What are those 12000 employees doing? It's not even evil. There is no conceivable way this arrangement can play out in Adobe's favour. It seems like a committee had a hand in this...