Pausing a pact, or putting it on an open-ended freeze, can be done by going to Settings > How to adjust my pact > Pause a pact. Swipe left on the pact you want to freeze. REMEMBER! The freeze will begin on the following Monday at 12:00am. You cannot freeze a pact in the middle of the week.
Here's a how-to video for more help! http://youtu.be/3MwdZNlAYfk