If you start offering a service like ProofHQ.com that works directly with acrobat I would be extremely happy. 

Designers point of view:

Create PDF. Open in Acrobat. Tell it to post to Acrobat.com and email a list of recipients to review the pdf by x date. As the owner of that PDF I can see who has reviewed, made changes and/or approved. Or an email is sent to me when all recipients have reviewed. From login you can see a list of documents you have sent out for review.

From the reviewers point of view:

They receive the email, log in to acrobat.com and there's a list of all the documents they have received to review and their review due dates. Once they've selected a file to review they can do comments and mark ups, with those comments tagged as being from that specific user. If they don't review by the date specified they receive a reminder email.

If you really wanna be schnazzy have the option to place an icon in the menu bar that gives an at a glance look at the number of pdfs sent or to be received and one click access to launch to the website and login.