You can tell at a glance which job postings are active and which are offline by looking at your dashboard. You'll see in the Applicant Analytics at a glance section the number of total active vs. archived job postings. 

To see which specific job listings are active and which are offline, click the box to the right of Filters: in the bar above the job listings on your dashboard page. You can filter by Online, Offline or Online & Offline jobs.

For more information on how to take your job offlineclick here.