Do you mean merge all pages from a section into one uber page?
There is no automatic(designed) way to do it. But if the content has no
noteflags and you don't care about positioning you could publish all pages
from the section in a single MHT file then copy paste from it onto a new
page. I wouldn't recommend this unless the source pages have very little
content each.
Just curious, why would you like to do this? Are you working on
consolidating Side Notes?