If you've signed up for DocHub Pro and are eligible for a free trial, then if you can cancel anytime before the trial ends, you will not be charged.
If you're using DocHub pro as an individual user, you can cancel by downgrading to the free version from the plan selection page:
If you're using DocHub Pro as an organization, then are available here:
dochub > your organization > settings > billing > change plan
or from https://dochub.com/organization/your-organization-slug/settings/billing/update-plan
where your-organization-slug is replaced with your organization's slug or domain