My vote also for briss. It was the simplest, fastest and did exactly what was required.
I wanted to convert few scanned pdf files written in Urdu, my native language. For easy scanning most of such books are two page up scan. Reflow can not work and zooming and panning in eReader is pain.
I very conveniently converted such files into single page PDFs. More so, I was able to crop it to discard border and have max font size.
It also allowed me to have slight overlap on gutter/ binding, to ensure text is not cropped.