'8.2. Database upgrades' section of JBPM Users Guide[1] is out-dated because it explains about using upgrade.scripts.
But when you upgrade from jBPM v3.1.x to v3.2.x, you need to follow a section about upgrading database schema in JBPM_3.2.x_x.zip/jbpm-jpdl-3.2.x/release.notes.html instead of [1].

[1] http://www.redhat.com/docs/en-US/JBoss_SOA_Platform/4.2.2/html-single/JBPM_Users_Guide/index.html#databaseupgrades