Create proof with multiple documents within Document area

We want the ability to combine multiple Workfront Documents into a single Proof. Currently, combined proofs can only be created from a local file upload. We have more than one contributor to some of our collateral, so each adds their documents to the Project's Document library. When a proof is generated we need to "add the collateral together into one proof for our reviewers. Please add the function to also upload from a project's document library.