بسم الله الرحمن الرحيم
(Fatwa: 653/653/M=07/1437)
It is unlawful to help in a job which involves interest and sin. In the question mentioned above, if your task is to prepare the documents and papers of interest based dealing, then it is not acceptable, you should quit the job. If you fear to fall in unbearable troubles in case you quit the job immediately then keep on searching halal job. However, you may continue with this job due to compulsion until you find an alternate halal job, provided you will quit this job when you find a lawful job and keep on doing taubah and istighfar.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband