In addition to filing a required Form S-1 (Registration Statement), many companies also file a prospectus with the SEC when they have an IPO or new corporate bond offering.
The purpose of a prospectus is to describe the securities a firm is offering. It typically provides material information needed in order to make a decision about investing, including a description of the company's business, financial statements, biographies of officers and directors, detailed information about their compensation, any litigation that is taking place, a list of material properties, etc.
Use the SEC's publicly-available EDGAR system to search for prospectuses, as well as other kinds of filings.