She taught English and received a master's degree in library science from the University of Kentucky in 1971.

Marcum graduated from the University of Maryland in 1991 with a doctor of philosophy degree in American studies.

She served as Dean of the Catholic University of America School of Library and Information Science from 1989 to 1992.

She retired in 2016, succeeded by former Vassar College president Catharine Bond Hill, but continued to work for Ithaka S+R as a senior advisor for educational transformation and libraries and scholarly communication until her death in August 2022.

[9][13] In 2013, she was appointed to the Japan-US Friendship Commission, which facilitates cultural and educational exchanges between the United States and Japan.