in the webassist/themes/Purple/css/purple_styles.css you can add more bottom padding by editing:
#main .content .ps_pod2, #main .content .infoWrapper, #main .content .productWrapper {
margin: 0 0 20px 0;
overflow: hidden;
}
to:
#main .content .ps_pod2, #main .content .infoWrapper, #main .content .productWrapper {
margin: 0 0 40px 0;
overflow: hidden;
}