If you wish to download the original files uploaded by a vendor, you first need to navigate to the relevant Project Page.
Once there, scroll down to the Submissions section and click to expand.
Under Active Submissions find the vendor you wish to download the submissions for and click the 'Actions' dropdown menu, as shown below.
When you click on Download all Files, Bonfire will automatically create a zip file containing all of the documents belonging to the vendor's submission and initiate a download. Note that if a particular file has been amended, you will have access to BOTH the amended file as well as the original. Depending on your web browser you may be prompted to accept the download before the zip file is downloaded.