Are documents posted online legally binding?

My employer has changed the employee handbook. I have been asked to sign a document that acknowledging that I’ve received the new handbook and have read it. The only place this document exists is online. I do not feel that I have received anything. In particular, there is nothing to stop intentional or unintentional modification of the new electronic only handbook with no notice to the workforce. Have others dealt with similar issues relating to legal documents that only exist electronically?