From My Ad Manager you can pause or resume a live campaign, or edit a campaign that isn't currently live — even while it's still awaiting review.
A live campaign can only be paused, never deleted, until it's finished — this protects viewers from a creative disappearing mid-flight and keeps billing accurate.
Spend accumulates per impression at your CPM rate. Once a campaign reaches its full budget it automatically ends and you're notified — no surprise overspend.
You'll also get a heads-up the day before a campaign's scheduled end date, and a low-wallet-balance warning if you're paying from your wallet and it's running low.