I depends on what your drop down is. Is it an enumeration value? Or is it an association to a list? What activity are you using to navigate through these two pages? Is it the show page button or a microflow button?
In either case, I recommend using a microflow button to navigate through the pages.
If your drop down is an enumeration value, in the microflow from page 1 to page 2, use the change activity to set the value that you want, and then use the show page activity to display page 2.
If its an associated list, in the microflow from page 1 to page 2, set the association you want with the change activity, and then use the show page activity to show page 2.
In both cases, since your value on page 2, is based on the value from page 1, you can use an exclusive split in the microflow to determine which value to set for page 2.