Legal Question in Employment Law in California

First of all, an employer is not permitted to condition your receipt of wages on your doing anything but performing work for the employer. In other words, they can't hold your wages hostage until you sign something. Your wages belong to you, not to the employer.

Also, I am suspicious that your employer may be asking you to sign more than just an employee handbook. There may be an arbitration agreement in the handbook, which could limit your right to bring a claim against your employer in court for any wages (or other claims). There may also be a release of claims in that paperwork, which could also limit your right to make claims against your employer.,

You should review the "handbook" with a lawyer before agreeing to sign it. Many of us offer free consultations.