。
I am enclosing our company brochure.
Literal
Our-company's company-guide [object-を] enclosed humbly-do.
同封いたします is 'I humbly enclose' — 同封 (enclosure) + いたす (humble する). 会社案内 is 'company brochure/guide.' This is standard business letter language — concise, humble, and formulaic. Every element serves the keigo framework.