You may find it useful to add a custom message on the "thank you" page for online bookings. This may contain information about finding your practice, or a link to new patient paperwork.
Navigate to Settings->Diary Settings->Online Bookings. In addition to the settings for online booking you'll see a textarea on the page titled "Custom confirmation page message (can include html):"
Enter whatever message you'd like people to see. E.g. Thank you for your booking. If this is your first visit, please download and complete our new patient paperwork, available by <a href="link_to_your_paperwork">clicking here.</a>