The best PR strategy is to gain articles written by online publications that people read, sending both referral traffic and helping improve rankings. Press Releases can work within industry--if the brand is major and niche industry publications are going to pick it up. A recent example: StarWars.com did a press release on Colin Trevorrow leaving Episode IX. Link: http://www.starwars.com/news/a-statement-regarding-star-wars-episode-ix This article is referenced and picked up without even having to go through a PR service because it's a major brand in the entertainment industry that's going to have a lot of coverage by movie blogs, vlogs, and so on.
All the above is to say, work on creating articles that can be featured on major news services. They'll have their own take that they spin for their audience, but you'll have a lot more traction from being featured on sites that refer you interested visitors versus a press release service.