I believe the exit interview is not in the best interests of the exiting employee, so my answer to this question is always no. Bear in mind that I'm not a lawyer and I don't pretend to give legal advice. Having said that, I also caution against signing anything.
Human Resources may invite you to participate or may issue something that sounds more like a command, but you do not have to participate in the exit interview. The most basic theory is that HR wants to you to reveal issues they may not know about. Further, the hope is that HR will do something about the problems inherent in (let's face it) any organization.
But an exiting employee has announced their disinterest in working further with an organization and no longer has a personal interest in seeing the company change. So HR may discount any "bad news" delivered during an exit interview as sour grapes on the part of the departing employee. If they want to improve the organization, they might be better served to ask employees who are still committed to the organization.
Also, everything you say or any survey answers you reveal during an exit interview will be noted and kept in a file. If there is any desire on the part of either party to litigate, everything you say can and will be used against you if it will strengthen their case. Again, I'm not a lawyer.
You may think that not attending an exit interview will reflect poorly on you and that may be the case. You can burn bridges by attending and by not attending. The decision is up to you. But as I see in interviews in my office, it is difficult to hide anger, resentment and bitterness, especially when those feelings are fresh.
If you do attend an exit interview, keep your comments short, sweet and simple. Above all, keep everything positive. Don't give in to the desire to tell them just how poorly they treat people, how bad management is, what awful policies they have in place or any other issue that is burning on the tip of your tongue.
The success of the organization doesn't actually rest in your hands.