To open one or more documents as Read Only, select the document(s) and click Read. This can be used for Emails and/or documents.
It allows you to open the emails and/or documents for read only without locking them from other users for edit access. They open in separate tabs in your browser. This allows you to tab through the open emails/documents.
In FYI, select the document(s) you want to read in one of the lists. For information on how to select multiple documents, refer to Selecting Documents in a List in Using the Documents Lists.