I know that you can't pause contributions from within CiviCRM with processors that aren't token-based - but can you with iATS?
If you can't do it within CiviCRM, can it be done from within the iATS portal?
Yes and No.
Here's two options:
if you want to Pause for a specified period of time (say 6months) -> hit Edit on the Recurring Contribution and advance the next scheduled contribution date by +6months.
if you want to pause indefinitely -> you could hit Cancel on the Recurring Contribution. And then (later on when ready to "un-pause") -> set the Recurring Series to In Progress again [that can not be done via the CiviCRM UI, but using API Explorer or with direct database access it's a simple query).
No pause on the iATS side of things.