With most modern browsers one gets given a choice whether to save the file or open it. Depending on how the browser is set up, the file may be automatically opened. That's on Windows, Linux and most likely also Mac.

How easy it is to get a pdf will depend on the technology one uses. With Grails, which I use, it is quite easy, provided the page to be turned into pdf is valid xhtml. Why do things the difficult way if there is an easy way to get the same results?