PMD uses Maven and requires at least Java 10 for building. You can get Java 10 from Oracle or from the OpenJDK Project.
PMD uses the maven wrapper, so you can simply build PMD as following:
./mvnw clean verify(on Unix-like platform such as Linux and Mac OS X)mvnw.cmd clean verify(on Windows)
This will create the zip files in the directory pmd-dist/target:
cd pmd-dist/target
ls *.zip
That's all !
Note: While Java 10 is required for building, running PMD only requires Java 7 (or Java 8 for Apex and the Designer).
cd docs
bundle install # once
bundle exec jekyll build
You'll find the built site in the directory _site/.
For more info, see README in docs directory.