PDF995 has worked fine for me for many years. It's free and is minimally invasive; each time you create a PDF it opens a window asking if you want to continue to use the free version or if you want to buy the software. All you do is close the window and you are back to business.
Of course the primary paid alternative is Abobe Acrobat, the original PDF software. For students and educators it's available for $116. A standard version is $280 and the Pro version is $430.