Is there a way to update a Collection that was based on a Zotero import without having to create an entirely new collection? We have a bibliography that is growing quickly and I'd rather just merge new Zotero data with it rather than recreate it each time.
Also, will Zotero import include attachments such as PDFs when you do a Zotero import?
There isn't a way to update the collection, like you can with an OAI-PMH import. But you can batch edit in admin and one of the batch editing functions includes editing collections. I've done this recently and it works out pretty well even though there is an extra couple of steps involved.
Go to the newly-imported items, change their collection and then you can delete the newest collection created by that latest Zotero import.
Files will be imported but you need to generate a private key from the Zotero library settings, and then use that in the Zotero Import plugin panel. The key is available from Zotero.org and the must be set to allow third party access. More information about this process is in the plugin's documentation page: