Is "docu" an acceptable clipped word for "document?"?

Hello, I'm learning about clipping words such exam for examination, dorm for dormitory, and phone for telephone. I'm confused as to whether "docu" or "doc" are grammatically acceptable clipped words for "documentary." I have a hunch that these are only found in colloquial/informal conversation and in Microsoft word file extensions, not in formal writing. Any help would be appreciated!