Recent change notes:
Fixed issue with custom rulesets on Unix.
General usage instructions:
PMD Plugin integrates PMD (http://pmd.sourceforge.com) to intelliJ. It supports all the pre defined rulesets as well as custom rulesets. The user can run pmd on a single or set of files/folders and see the results in intelliJ. To run the predefined rulesets, go to Tools -> PMD -> PreDefined menu. PMD supports custom ruleset file, to configure goto settings -> PMD and add the rule set files that are required.