How do I print a very large document in excel. I need to print so the
columns are printed first and not the rows.

the question is ambiguous, but perhaps what you are looking for
might be file, page setup, sheets, where you can choose
Page order: down then over, or over then down

If you are doing duplex printing with two sheets wide then you
would probably want to switch to over then down.

I probably guessed correctly because after writing that, I noticed the wording
in the subject that was NOT included in the question. Please write a clear and
complete question that does not rely on part of the question being in the subject.