Distribution of PR pieces or articles. The problem here is with high value PR sites the content they publish is wide and varied and rarely applies directly to your industry. PR sites rarely allow you to control the link text in your PR piece. 
The PR of the page where your article is placed will be n/a or 0 (zero)  so there is little link juice passed on.  The PR site might have a high PR but the page the PR piece sits on is unlikely to have.
Work involved, a huge amount. Value , very low. 3/10