If you are running PDF Index Generator version 2.1 or an earlier version, and you have Java 8 installed on your computer, then you will mostly get an error message. This happens because Java 8 was released after version 2.1 was out, causing some errors with PDF Index Generator. This was handled in version 2.2 of PDF Index Generator, so version 2.2 now runs fine with Java 8.
We suggest you upgrade to the latest version of PDF Index Generator (https://pdfindexgenerator.com/download-trial) to overcome this, or downgrade to Java 7 (http://www.oracle.com/technetwork/java/javase/downloads/java-se-jre-7-download-432155.html) or Java 6 (http://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase6-419409.html) if you want to use an earlier version of PDF Index Generator.