Are you using a document that has been enabled for commenting?
We have many typewriter enabled pdf's in our office we use everyday. Adobe updated to Adobe Reader X 10.1.1 and I can make comments, but the typewriter option is not available and the support forums say to go the the right, go to Tools and go to edit. There are no edit options under tools, only create and send pdf files. Under Comment, I can put in a sticky note and highlight. I have brought up old pdfs that I have previously Typed into and it no longer shows up as an option on the old forms.
That would seem to indicate that Reader isn't seeing the document as being enabled for commenting. What does is show for the security restrictions under "File > Properties > Security"? Do you have an "Extended" option on the far right next to "Comment"? Sorry, I'm unable to test Reader at the moment.
No extended option next to comment. Security has
Security Method: No Security
Can Be Opened by: All versions of Acrobat
And in the Restrictions Summary, Document Assembly, Signing and Creation of Template Pages are Not Allowed, but everything else is Allowed. Thinking I'd better just delete this version and download a older version.