unfair

https://github.com/taunio/unfair-ruby

unfair is a small, dependency-free Ruby wrapper around the unfair native C ABI. It converts office documents between formats (txt, docx, odt, xlsx, pptx, pdf and more) using only Ruby's standard-library FFI (Fiddle) - no C extension, no compilation step. The native unfair_ffi shared library is loaded at runtime per platform.