Web to Lead Form With Two Different Free Reports

Web to Lead Form With Two Different Free Reports

I have two web to lead forms set up to receive leads' information and send them free reports. 

Each form is on a different landing page, and each subject is different.

I want to capture the leads AND know which lead is associated with which subject (free report).

All I see now in the notification to me (lead owner)  is the form information: First Name, Last Name, and Email address.

How do I indicate which report the lead received?

Thanks!