If you're looking for an adjective, try "pretentious".
The word "pretentious" generally has negative connotations: it is used to describe someone who is trying to seem more important, educated, or cultured than he/she actually is. See the FreeDictionary definition.
Also, regarding the additional context you provided: the sentence in your update gives me pause. First, "the way he spoke was not of a preacher's" is not grammatically correct. "Preacher's" is possessive (presumably modifying "way"), but you're also using it as the object of the preposition "of" (which also modifies "way"), so you wouldn't do both. You could try "the way he spoke was not that of a preacher", or, better, "he did not speak in the manner of a preacher".
Second, the word "preacher" may give the wrong impression. When I think of "preacher", I think of someone who conducts religious services and, in the context of speaking, delivers sermons. In the U.S., these sorts of preachers are not generally seen as pretentious or prone to using overly-complicated words, at least not by most Americans. In other words, the second sentence does not support the first.
Third, you used "pre-arrangement" and "citations". Citations don't have anything to do with a manner of speaking; a citation is generally a written thing. And I'm not sure what "pre-arrangement" means in this context.