Way back when the makers battled for your sale and cut deals to include added software like PDF creation. Today you get a scanner and not much else. If you need to scan directly to PDF you look at picking up Adobe software and see if your scanner is supported.
Or you scan then create the PDF later.
I'm skipping on writing about the HP 4050 since you can get all the details at hp.com and maybe Cnet's review.
But one Amazon review at http://www.amazon.com/review/R7SEQ6L1KVPYM makes me think you are looking at a very nice scanner since they used it on their Apple!
I had an HP 3200 scanner which worked well for years. Now, I have to replace it since its driver is not compatible with Vista on my new PC.
I've read lots of reviews--some of which say that a scanner such as the HP 4050 won't work w/Vista or won't convert to PDF.