Refund please? It is of no use to me

How do I cancel this product and get a refund?

All I wanted to do was to reduce the size of a PDF down from 18MB so that I could email it.

I paid £19 and I cannot do what I want.

It is very hard to navigate to navigate your site and find a place where I can cancel or complain.

I managed to reduce the size by re-scanning in black and white

Thanks