I am not clear on why you mention RoboHelp Server as that is not really intended to SME reviews.
My own preference was always to generate a Word document as most SMEs found that easier to edit. I trained them to preface any change or comment with three hashtags. ### Then I would search the document for those hashtags and deal with them.
There is a review process using PDF built into RoboHelp 2017 but that came after I had instituted the Word method so it was easier to continue with that. "It ain't broke so don't fix it."