FWIW...
1 thing to remember when talking about, rating, trying PDF conversion &/or editing software, is that there are several ways, programs to create PDFs now days -- the PDFs created are not always the same internally. What works for PDFs created in one program might fail miserably on the output of another. There are quite a few cheaper PDF conversion programs out, but in my experience how well they work, or if they work at all depends on what created the PDF you feed them. A few examples with ratings/comments for Quick-PDF [http://www.quick-pdf.com/] can be found here [http://www.giveawayoftheday.com/category/quick-pdfcom/].
FWIW RE: Serif...
AFAIK -- & from what I can recall (which may not be *totally* accurate) -- Serif was started years & years ago by Russian coders going up against Adobe & quite possibly Aldus (it was that long ago) (assuming anyone else is old enough to remember Aldus). They had excellent products, but not a lot of marketing clout in a then very closed-minded publishing & graphics arts community, where it was felt your professional credibility rested on the price of your tools, not your results. I think they then started licensing code or collaborating on niche products like a vector-based Dinosaur Drawing program one of my boys used back in a grade school project, eventually I believe turning over marketing (or selling themselves?) to one of the mass marketers similar to Broderbund. Their initial DTP program was dumbed down a little to compete with the brand new Microsoft Publisher, over the years becoming the PagePlus discussed here. You'll usually find deals on their software on various shareware &/or PC magazine sites like vnunet, at software surplus sites, at discount PC parts & accessory sites, & sometimes in the cheap software racks in retail stores.