According to Box Help, direct linking to files is only supported for paid accounts; however, I found that it is possible to link directly to a file with a free account. Just create your own direct URL using the following format
<SHARE_NAME> is the random alphanumeric string that is part of a share link. For example
https://app.box.com/s/sn5mfs7esv0w35ybeoa5. This standard share link takes you to a page where you can view an online preview of the file and click a download button to get the actual file.
<FILE_ID> is the numeric identifier for the file which appears at the end of the URL when editing the file. For example
The direct link for this example would be
Since this isn’t officially supported, Box may always update the service to prevent this.