Student or Learner
1. Someone returns to something as an editor.
2. Someone returns to something as editor.
Are both acceptable?
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Federman joined the AP in 1993 in New York. After a year, he was briefly transferred to Charleston, W.Va., but returned to New York as an editor and supervisor in 1995. In 2000, Federman began working as an editor at the Wall Street Journal, and was soon promoted to deputy technology editor for the journal's Web site.
Sheldon Drobny: Follow-up To Mamet's Post: John Carroll-Former LA Times Editor
He returned to Winston-Salem as editor and publisher from 1963 to 1973.
"an editor" implies that there are a number of editors
"editor" tells you that he is the only editor in this case.
The second example you give is referring to the person's position in a publishing company where he is a senior executive in the company. In this position it is more related to business practice than to the control of content and syntax.