Pagerank is one of the 200+ factors Google counts while ranking but it is not the DECIDING factor.
PR is no way related to traffic, its a performance metric!
You need to get quality backlinks in order to get PR.
Major reason for low traffic can be poor optimization of website and absence on social media channels. You need to promote your website on social media channels in order to pull traffic. Here are four killer tips from Matt Cutts himself
http://www.keywordcountry.com/blog/g...is-kidnappers/