What is the ruling on purchasing materials for a company at a reduced price, claiming they are for public sector companies, with papers issued to prove that, and is it obligatory to leave this job?

If the materials do not belong to a public sector company, it is impermissible to issue documents proving their sale to it, due to the deception, forgery, and unlawful consumption of wealth involved. If the questioner's work in the company obliges him to do so, then he is not permitted to remain in it except out of genuine necessity, where he cannot find another job and does not have the minimum means of livelihood, while continuing to search for a permissible job.