Spanish term (edited): adulteración de hojas

-> on the assumption that 1. adultación is a typo 2. the asker is not at professional liberty to divulge and disclose more info. 3. falsification (of documents : West) or counterfeiting (of non-currency) are not 'one size fits all' solutions and may not fit the context, scant as it is.

Doctoring (a translation in an SPA/ENG dictionary from an ersthwile languages bookshop near Liberty's on Regent Street and that used to serve me well) of audit, ledger folios or account pages - or sheets of notes to the accounts - may be nearer to that elusive mot juste /right word.