Adobe is currently testing a modified PDF online sharing feature with some users.
The current version is described on a web page:
On another web page the new variant is described:
The file to be share is uploaded to the Document Cloud and a link to the file is sent to the recipients by e-mail. Acrobat/Reader is no longer required to view and insert comments. All you need is a standard Internet browser. Recipients do not need an account in the Document Cloud either.
However, some definitions in print production files (overprint, transparency) are not displayed correctly by the Document Cloud Viewer. Therefore, caution is advised when using the Share function for approving demanding print production files!
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I must highlight the fact that overprint and transparency effects are still rendered incorrectly (same happens in Document Cloud). It means that to send for review PDF document, you must flatten all elements to be compatible with the 1.3 version, otherwise you will not know what user on the other side is looking at.