http://example.com/pages.php?pageNo=35

The variable here is the pageNo parameter.

You can download all the pages by adding a regular expression like parameter in the CURL url as given below.

curl -o pages#1.html http://example.com/pages.php?pageNo=[1-12]

This will download all the pages from page no 1 to page no 12 and save it to a corresponding file.