It's a little more complicated than that. Each page in the digital booklet, except for the front and back cover, has two printed pages. For example, db (digital booklet) page 2 has printed pages (pp) 2 & 3; db page 3 has pp 4 & 5; db page 3 has pp 6 & 7, etc. Each db page folds down the vertical center; if it were actually printed, there'd be two staples down that vertical fold. Also, a printed booklet has double-sided printed pages. Because only 42 booklet-sized pages are provided, this presents a problem because normally you'd need 44: 11 double-sided pages that would be folded down the center to provide 44 booklet-sized pages.
In order to actually print the db, the pagination would have to be as follows (ignoring the covers): db page 1 would need on one side pp 2 & 40, and on the other side pp 3 & 39. The next db (page 2) would need on one side pp 4 & 38, and on the other side pp 5 & 37; etc.
So to use Sejda, you'd also need to cut each db page down the center and then reorder those pages. It's a big mess.