Yes, it is possible to pause and enable a campaign in the AdWords API by just setting the
status to PAUSED or ENABLED. You can check the example
here in setting the campaign to PAUSED status.
However, for trial campaigns, it is not possible to update its status as this field is immutable based on this
link. Once you try updating it, it will generate a CANNOT_MODIFY_FOR_TRIAL_CAMPAIGN error.