What is needed in OS X web browsers

I'm experimenting with OmniWeb 5. It is a great web browser. It occurs to me though, as I'm still unable to read my bank statements with anything but Internet Explorer, and the older statements are n PDF format that the OS X web browsers need to be able to display PDF inline. Why can't they? PDF rendering is built right in to the OS... Is it a webKit shortcoming? Wherever the issue lies it should be addressed sooner rather than later.