It would seem you have already made up your mind not to sign it by your statement above, if you plan on staying with the company I see no reason not to sign, but if you do plan to leave it could be sooner then later if you refuse.
Kinda' a hard place to be in, you made them look bad (normal print staff) and good (with the customers) at the same time, I would think your employer has noticed that which is the reason he wants you to sign.....ultimately no one can make the decision for you.
Hope this helps.