how to protect confidential document

I am working for an auditing Business
The doc is actually an auditing process manual. It's a
600+ page manual of procedures that has "proprietary and
confidential" wording on every page. Our customer recently posted an
RFP for the contract we're working on, which ends in a year. There's
a fear in upper management that this document maybe forwarded to
potential competitors. Over 150 users need to view this document daily
for processing purposes, so they want to put some type of security
control in place.

I was thinking we put it on an internal webserver, where users have to check a disclaimer before they get to the actual document.
Of course that doesn't prevent them from copy/paste the thing.but at least they know of the importance of this document.

What ways are there to prevent them from copying the whole doc.
I am not talking about computer savvy people, just the "regular" office users.

any suggestions?

VV
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