We don't store any data used to generate the document or the generated document itself. We only store the template structure and any static text which is added to the template.
Making an API request to merge template and data is a “merge” action. One unique PDF/HTML generated through the API is counted as one “merge”.
The Sandbox account is a fully functional PDF Generator API account, which is free to use for the integration process and testing the service. Once you are ready to go production you can just upgrade your account and all your users and templates are available after the upgrade.
You will have a separate deployment that only serves your application without any monthly limits (fair usage) and you can use your sub-domain and custom editor theme.