It’s not possible to have two forms on one page, but there is light at the end of the tunnel as there are a few possible workarounds to get this done for you.
Create a second stand alone Unbounce landing page with just a form in it and then load that into the Unbounce native lightbox feature, allowing them to click a button and fill in the form ready for the download
Create an HTML form and embed it using the custom HTML block functionality that’s part of the page builder.
Setup a mailchimp (or similar) account and embed the form into a custom HTML block or load it into a lightbox, this will enable you to build a list by collecting email addresses then either make the form available for download on a thank you page or send it as part of the autoresponder series. This also gives you the chance to make sure people confirm their email address by clicking a verification link and continue to email market them. I bet you can guess from my reply that this is my preferred method. The value of list building is never to be underestimated.
There are tweaks and details that will depend on your setup, lead tracking etc to take into consideration but those are your quick workarounds.
I hope that’s of some help,
Feel free to ping back if you need any more advice.