The only payment option at this time is via credit card (debit or credit). The accepted payment methods include AMEX, Visa, MasterCard, and Discover.
There is no annual billing option at this time. An annual option is being considered and may become a reality in the future. Per our terms of service the current payment arrangement is a month-to-month subscription without any long term commitment. You can upgrade, downgrade, or cancel directly from within the account.
Here are our current pricing and plan tiers. All plans include unlimited users and are based on the amount of active projects and document storage needed.