Yes, you can!

When you create a package, there is an option to set the "Quantity."

If you set the quantity to a number greater than one, then after someone buys the package, they will see a link that says "Click here to manage your download tokens."

(They can also see an option to manage their download tokens if they select the book in their Leanpub library.)

There, they will see a form that lets them use each participant's email address to send them an individualized code, with instructions for how to redeem the code.

You can create a package here in the Leanpub menu:

Author > Books > [Your Book Title] > Store > Packages

Here is an article about how to create a package.