What happens to contacts in my workflow when I pause it, and to contacts who meet the trigger while it is paused?

When you pause a workflow, no new contacts will be added to the workflow and contacts already in the workflow won’t flow through it. Everything will pause. As soon as you relaunch the workflow, new contacts who meet the enrolment criteria will be added to workflow and all contacts already in the workflow will continue the journey where they left off.

Your workflow sending settings (which days and times to send) will determine when the messages are sent.