How to cut each page of a PDF or DJVU file into halves?

Question

Say I have a book (either pdf or djvu format) where every page looks like this:

Is there any way to cut separate the two pages? I want to print things on A4 paper, but scaling it down by a factor of two sometimes makes the text difficult to read.

Answer 1

Try BRISS. It lets you hand-select multiple regions of each page to divide into new pages.