'unredacted' is formed in modern English by adding the prefix 'un-' (meaning 'not') to 'redacted' (the past participle of 'redact').

'redact' comes from Latin 'redactus', the past participle of 'redigere' (to drive back, bring together). It passed into Old French/Medieval Latin as words like 'rediger'/'redactare' and into English as 'redact' with the sense of preparing or editing a text; 'redacted' (past participle) later combined with the prefix 'un-' to form 'unredacted'.

Originally related to gathering or bringing together text (Latin sense), 'redact' shifted to mean preparing or editing a text and later 'to remove or censor parts of a text'; 'unredacted' therefore means 'not censored/edited'.