Ah, this old chestnut! PageRank used to be one of the sacred mantras you would hear SEOs chanting. Your PR was of huge import and anyone with a PR of 5 or above felt they had the right to look down upon you. Some people lost sleep whenever their PR dropped, or if they had tried everything and still had a PR of zero.
PageRank came into being to help Google assess pages for authority, backlinks etc. It is never quite clear if the mystery surrounding how PR was calculated was solved, but over the years, PR slid down the ranks in algorithmic importance.
Until, on Oct 14th, 2009, Google finally said very clearly and in a manner that was not up for further debate, that SEOs could all sleep soundly again and PageRank, just as they had been trying to tell anyone who would listen for quite some time, was really, really not important. In fact, it had been removed from Google webmaster tools.
So, when anyone tells you to look for sites with a high PR, or to spend time trying to increase/gain PR, you will know better!