You can edit Active, Pending, Pending, or Ended campaign.
To edit your campaign:
Go to the Campaigns section and locate the campaign you want to pause in the Campaigns table.
Click on the 'edit' button - you'll be redirected to the editor mode.
Make your edits and click the 'Submit changes' button in the top right corner.
Note: Editing some settings will require a re-audit of your campaign, so changes won't be immediate.
Editable campaign settings:
Advanced Targeting Settings
Landing page & creatives
Optimisation strategy (CPM, CPC, CPA)
Campaign model (Prospecting, Retargeting, Contextual)