To redact (pronounced re-DACKT) is to bring together, combine, or organize writing; to edit text for publication. It is a nineteenth-century back-formation from redaction, which can be the process of editing or a version of a text, such as a new edition or an abridgment.
The French redaction, which English adopted and naturalized, rises from the late Latin redactio, ultimately from the Latin redigere, "to bring back."
The word has become familiar to a general audience from its prevalence in describing what is done to official documents sanitized before making public; in this sense, the redacting involves deleting sensitive information.
Example: Redaction as deletion is exemplified in this passage from Wanderer in 1994: "But most disturbing is a confidential memo Ickes sent to Hillary Clinton on the RTC, which has been redacted from 25 pages to one paragraph."