I’ve got a number of documents, all of which have a bibliography, and all of the bibliographies have to be formatted in the same way (e.g. journal entries go: number: authors. Title. Paper, volume, pages). Is there a way of copying this formatting between multiple documents, or do I have to format each bibliography manually?
My hunch is that this will need to be done manually. You don’t say that a bibliography or citation manager has been used which might have automated the process. One option would be to enter all the data into such a database (Zotero, or the like), and then output the results to your final bibliography.
Are you compiling a cumulative bibliography? or will the separate documents each keep their own reference list in the collection? If the individual bibliographies are very consistent, then it might be possible to do some careful and judicious bulk search/replace operations to bring the conformity you need.
Otherwise … put on some quiet music, a big pot of coffee, and start editing… 
I’ve used libreoffice’s bibliography database, but not zotero (the plugin doesn’t work on my computer, so I decided to input the citations manually).
And the separate documents each keep their own reference list.