Here is paypal's instructions on HOW TO opt-out of the policy amendment in question.
Opt-Out Procedure.
You can choose to reject this Agreement to Arbitrate ("opt out") by mailing us a written opt-out notice ("Opt-Out Notice"). For new PayPal users, the Opt-Out Notice must be postmarked no later than 30 Days after the date you accept the User Agreement for the first time. If you are already a current PayPal user and previously accepted the User Agreement prior to the introduction of this Agreement to Arbitrate, the Opt-Out Notice must be postmarked no later than December 1, 2012. You must mail the Opt-Out Notice to PayPal, Inc., Attn: Litigation Department, 2211 North First Street, San Jose, CA 95131.
The Opt-Out Notice must state that you do not agree to this Agreement to Arbitrate and must include your name, address, phone number, and the email address(es) used to log in to the PayPal account(s) to which the opt-out applies. You must sign the Opt-Out Notice for it to be effective. This procedure is the only way you can opt out of the Agreement to Arbitrate. If you opt out of the Agreement to Arbitrate, all other parts of the User Agreement, including all other provisions of Section 14 (Disputes with PayPal), will continue to apply. Opting out of this Agreement to Arbitrate has no effect on any previous, other, or future arbitration agreements that you may have with us.
Future Changes to the Agreement to Arbitrate.
Notwithstanding any provision in the User Agreement to the contrary, you and we agree that if we make any change to this Agreement to Arbitrate (other than a change to any notice address or website link provided herein) in the future, that change shall not apply to any claim that was filed in a legal proceeding against PayPal prior to the effective date of the change. Moreover, if we seek to terminate the Agreement to Arbitrate as included in the User Agreement, any such termination shall not be effective until 30 days after the version of the User Agreement not containing the Agreement to Arbitrate is posted to
http://www.paypal.com, and shall not be effective as to any claim that was filed in a legal proceeding against PayPal prior to the effective date of termination.