Prior to his appointment, he was DENR Undersecretary for Field Operations and Executive Director of the Minerals Development Council under the Office of the President in concurrent capacity.

Paje is a holder of a doctoral degree in public administration and a top-rank Career Executive Service Officer (CESO I).

In 1999, he was the Dr. Jose Rizal "Huwarang Pilipino Awardee" for public service given by the Parangal ng Bayan Awards Foundation.

Dr. Paje served as Secretary of the Department of Environment and Natural Resources (DENR), under President Benigno S. Aquino III, from 2010 to 2016.

As DENR Secretary, he implemented major programs and policy reforms which the present government continues to carry out up to this time, to wit: Total Logging Ban in Natural Forest.

The precise determination of flood-prone and landslide-prone areas in geohazard maps greatly enhances the country's disaster preparedness and saves lives.

Secretary Paje signed for the Republic of the Philippines the historic Paris Agreement on Climate Change on April 22, 2016, at the UN Headquarters in New York, with world leaders and other environment ministers.