Thanks for reaching out. The free program of PDF Tools API is for evaluation purposes only and is not recommended to be used for commercial purposes. The free quota enables you to use PDF Tools API capabilities for a limited number of operations i.e. 1000 PDF Transcations, the paid program enables a greater processing quota and require entering into a separate written agreement. For more details on both the programs, please refer PDF Tools API Licensing section under PDF Tools API document in https://www.adobe.io/apis/documentcloud/dcsdk/docs.html.