If my employer recently re-wrote the employee handbook/company policies, are they required to have all employees sign the new document to acknowledge the changes?

It is not a legal requirement that employers have workers sign the employee handbook, although it is a good idea since the handbook outlines the policies of the company. Further, employers don't have to require employees to sign an acknowledgment whenever an updated handbook is distributed, but again this would be a preferable practice.
The purpose of a signed acknowledgment is to demonstrate that the employee has not only received the handbook but is also responsible for knowing the information contained within it. Although, employees sometimes misunderstand that by refusing to sign the acknowledgement form they are still held accountable for complying with their employer's policies. The acknowledgement form simply demonstrates the receipt of the information and not compliance with policies.
Finally, while an employer cannot force an employee to sign the handbook, if an employee refuses to do so, it is possible for an employer to view the refusal as insubordination and terminate the employee. At least so long as the employee has no protection againts this action pursuant to an employment contract or union agreement. Additionally, if an employee is terminated for not signing, their treatment cannot constitute some form of actionable discrimination or retaliation.