An "embargoed copy" refers to a document or information that is not yet intended for public release. It is shared with a select group of people who are given access to it before it becomes available to everyone else. Full definition
To get their work before a broader audience, they shared embargoed copies of the documents. (insideclimatenews.org)
The Lib Dems released embargoed copies about half an hour ago. (theguardian.com)
It would have been very helpful if members of the Policy Working Group had been sent an embargoed copy of the speech the night before. (conservativehome.blogs.com)