You can use an opt-in checkbox on any signup page to give your listeners the opportunity to signup for a second signup page without having to fill out their information again.
The Opt-In Checkbox is available at the bottom of the Standard Questions section when creating/editing a signup page.
Just click & drag the Opt-In Checkbox field into your signup form. Once you drop it in, it will give you a pop-up to select what other existing signup page in your station they can have the option to signup for.
Once it is in your form, the default text will be name of the signup page you selected.
You can update this text to make it more clear to your listener what the checkbox opt-in is for.
Once you save your form, it will now appear as a single checkbox. If the listener checks this box before submitting the current form, they will be added to both the form they're filling out & the signup you selected as the opt-in.