Netflix accepts PayPal as a payment method if it is available in your region. If you do not see PayPal as an option when signing up or updating your payment method, PayPal payments are not available in your region at this time. Feel free to check back periodically to see if this option becomes available.
If you are having trouble getting Netflix to bill through your PayPal account, PayPal can provide the most up-to-date information on the types of payment they accept for Netflix transactions in your region.
If you need to update the payment method on your PayPal account, PayPal.com can help you with that as well.