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.