This is not close to something I would call THE solution, due to a number of factors (I will play down my own answer itemizing these below).
But it is the closest I got when trying to do the same thing!
In particular if trying to change the view on-the-fly.
You need Microsoft Word (#1).
Open the pdf file. There may be some things that do not show up exactly as in the pdf, in particular if it has many images (#2).
But it may give you a good bird's eye view of the document, which may be your main target given that having several pages side-by-side does not allow for much more than this.
Multiple pages (in Spanish here).
Then set the
Zoom level that gives you the number
N of side-by-side pages you want, depending on your monitor size and resolution, and Word reading pane size.
Say you have 3 side-by-side pages at the current zoom level, your pdf will be displayed 3 pages per row, and you will scroll down across this layout.
You will not be scrolling horizontally across pages in a continuous manner (#3?).
This may or may not be what you want.
Generate a pdf N-up file.
There are a number of ways to do this. It will create a "fixed" view (with fixed number
N of side-by-side pages), and you would have to generate a new pdf N-up for each
Adobe Acrobat allows for this printing.
There is also
pdfnup. I do not have MacOS, but I guess it should work.
Its advantage over Adobe Acrobat is that you can do batch processing. This may make your life easier.