Among the features:
Expand the scope of PDF-based reviews by filtering topics based on the table of contents (See screenshot)
Include dynamic HTML content in the workflow
Review expanding and drop-down text and import comments related to them
Track changes
A crucial need for writers is to keep their authoring colleagues and Subject
Matter Experts "in the loop" so that requested changes can be
synchronized during development. Review and Collaboration workflows using
Adobe technology make this possible. All the reviewers need is the free
Acrobat Reader software.
A major benefit is that you can send all or just a few of the topics in
the project for Subject Matter Expert review.
The Create PDF for Review is accessed from the Review menu.

There are three ways to create a PDF Review.
Create A Local PDF
Creates a PDF and saves it to a location you specify. You then distribute the file by your preferred means.
Attach For eMail Review
Creates a PDF and attaches it to a new email message opened in your email client. You can complete the message and send it to the reviewers.
Send For Shared Review
Creates a PDF and uploads it to an internal server or network location for shared review. This option requires that the initiating RoboHelp author has Acrobat XI Pro or higher installed. The reviewers need only have the free Acrobat Reader.
After all the reviewers have made their comments, the author then uses the Review > Import Comments from PDF command. A Review Pane opens and shows a list of reviewer names and the particular comments or changes they are suggesting. By double clicking the comment, the author can conveniently go to the particular topic and elect to accept or reject the comments either all at one time or one by one.
To keep your content synchronized, after creating the PDF you must not make any changes to the topics being reviewed until you have imported the reviewer's comments.
PDF based review is described in more detail in the RoboHelp online help.