By going to the 'Payment Request Details' screen of the agreement you wish to pause you'll see the agreement field has a 'Halt' option.
A window will pop up informing you:
'You can halt an agreement from today's date or a selected future date. This will delay but not cancel payments.' Choose whether to halt immediately or choose the date you wish to halt the agreement on.
You can choose to leave the 'halt' in place until you wish to resume, or, you can have the payment auto-resume after a specific time frame that you can set here.
When a halt is ended and payments are resumed, the first payment will occur according to the original schedule.