I am using the ACM tex template
sig-alternate.cls downloaded from this page, Option 2: LaTeX2e - Tighter Alternate style.
This page provides the minimum working environment, including files in the following figure.
I downloaded all the files and compile them with the CTeX suite (WinEdt 6, MikteX 2.9), the generated output PDF file has very large space at each page bottom, which differs from the original PDF on that page. My own generated PDF file can be found here, and the PDF provided by the ACM website is here. You can compare them with each other.
I am wondering why the page bottom space is so large when I used
sig-alternate.cls, and how can I reduce the space.