It's not possible through a single account to pledge to more than one reward per project.
However, there are two options:
1. If you have two email accounts, simply sign up as a guest or create another account under the different email and re-enter your payment information as you make the pledge.
2. Add the pledge amounts together and manually change it as you pledge to one of the rewards. Then forward us your pledge confirmation with a note to firstname.lastname@example.org letting us know you wish to have both and we will fulfill your order properly once the campaign ends. (Example: If you would like to receive "All three videos"($147) and then also sign up for a workshop with one of the artists ($590), just add the two together 147 + 590 = $737 and manually type in this amount as you pledge to the workshop reward.)
Please email us at email@example.com with any questions.