I'm not sure about converting to PDF, but GoodReader can certainly save the webpage for offline viewing (in GoodReader - which incidentally can view many different file types including PDF, super handy!).
Just install GoodReader, then in Safari open the page you want to save, and append a "g" to the URL (so it's ghttp://) and it should save into GR.
I'm not sure if you might have an issue with it being a protected online banking page though, come to think of it.