The LinkedIn Limited Listings settings is a job board setting, instead of an individual job post setting. This is why the LinkedIn Limiting setting can not be edited directly from a job post.
This LinkedIn Limited Listings setting can be edited by going to Configure>Job Board>and selecting to edit the Job Board. Here you can select whether or not you would like to turn on LinkedIn Limited Listings for all external, live jobs on the job board.
Applies to: [Users that can edit job posts]
Keywords: [LinkedIn Limited, Free job post, edit job post]