I would consider Hellion's suggestions: to rephrase the statement.
Yet, if you still want to maintain the style you provided, you must use a reflexive pronoun because in imperative sentences, you are addressing someone, who is normally "you", even though this subject is hidden. So, that's how you would read it:
You please have the president...
Therefore, since the subject you is there and you are referring to him/her, then the reflexive pronoun must be used:
Please have the president and yourself sign the document.
That's how it is theoretically read:
You please have the president and yourself sign the document.
(yourself) referring to the first and hidden subject (you).