PR articles are placed on Web sites, specifically designed for that purpose, or also on industry-related and thematically-connected quality websites. So they have their meaning. Placing on some poor quality pages does not matter, and on the contrary, it could harm your site.
PR articles contain also backlinks. They are therefore an important part of linkbuilding, thus building a network of backlinks. Linkbuilding helps increase the popularity and attendance of the site, and increases its position with Internet search engines.
Normal text appearance
But the Pr articles should definitely not look like internet advertising. In that case, many people would not be interested, and few would read them. The appearance and content must match the usual informative text, and the ad should be hidden and non-violent. It just fulfills its function.