To specify a set of official, built-in rulesets to be used set them in the property maven.pmd.rulesets. You can include this setting in your project.properties file.
A clean strategy for customizing which rules to use for a project is to write a ruleset file. In this file you can define which rules to use, add custom rules, and customizing which rules to include/exclude from official rulesets. More information on writing a ruleset can be found here.
Add to the root of your Maven project a pmd.xml file which contains the ruleset mentioned in the previous paragraph. Add the following property to your project now:
maven.pmd.rulesetfiles = ${basedir}/pmd.xml