Well, it depends on the context. In some cases there's no difference between pass and pass on, while in others there is. For example:
"Scotland Yard's phone-hacking squad has passed on the files of two police officers in relation to misconduct in a public office"-- HuffingtonPost UK
"He passed the files to his colleague, Heather Clark, who is writing a Plath biography and who will present a paper on them at the symposium."-- Guardian
In the above examples both pass and pass on mean the same thing.
There are many different uses of pass on that can mean different things in different contexts. But in your specific example, pass on means
to transmit (knowledge or skills); "give a secret to the Russians"; "leave your name and address here"; "impart a new skill to the students"
and is semantically different from pass.