It is a common practice of building do-follow links with many strategy while linking and reputation of the site from where links come. Today, although technically it was true, all the time, implementation levels were lacking, has become very important ranking factor. Because if one just make sure that links coming from high PR site as the only criterion, he is mistaken. It is very essential the page authority from the page from which you get back links. , so one has to think of multiple ways of building page authority of the pages from where they acquire back links.
check this
Domain Authority & Page Authority Metrics - Whiteboard Friday
check this
Domain Authority & Page Authority Metrics - Whiteboard Friday