Easiest way to do this is to not sign anything unless it involves extra pay. I’ve politely refused HR’s request to re-sign bunch of documents before when leaving - I didn’t feel like digging through them or paying a lawyer and they had zero leverage
I've never refused, but I do always outline the (usually low four figure) cost in time and legal expenses required to review the contract. I close by explaining that I cannot in good faith enter into an ostensibly binding contract without some form of consideration from my counter-party because such a contract would be difficult to enforce in any case.
HR never knows what to do and usually just never gets around to replying to the email.
I had signed a contract at hire saying I would sign the separation agreement when I left.
I didn't have any issue with the agreement I had already made. I just wasn't willing to change it as I was voluntarily leaving and they weren't offering me anything to change the terms.
I'm not even 100% sure I would have noticed it except that my new employer required disclosure of any restrictions I had, so I disclosed the 12-month non-recruit from the previous company. It was fresh to mind.
The two companies are in the same general industry, but do not compete with each other.
I don't even politely reply. At my last job, HR sent me a "contract" offering $1 in exchange for agreeing not to work in the industry for 1 year. I archived their email and never spoke to them again :)
It would really depend on the job, of course. I didn't really care about that one, and didn't see myself ever wanting to work with that founder again, so I didn't make any effort to be "nice" in any way. If I ever left my current job, I would make sure to stay on the best of terms. I would be annoyed if they paid me $1 to not work for a year, but I also know they would never ask for that.