No, it's not necessary. They contain code that's used by the various tools (java, javac, javadoc, jar, ...) and other stuff used internally by the JVM. But the JVM knows how and where to find these jar files, so you don't need to worry about them.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com