This is something that could be easily added with a server side script (PHP, Perl, etc.). The PDFE web server can host these languages engines, and the script would be responsible to generate a share file URL, served by a script used to check the URL validity and file delivery. The script can be extended with functionality such as number of downloads possible, download expiration date, etc..
If I get some time I will try to code it, and post it here as example.
Anyway, having this functionality readily available from the web interface may be handy, so I've coded a new web interface API function, GetFileShareURL, and integrated it in the advanced (see attached image), and standard HTML, web interface clients. This way a web interface logged on user may grant access to a document with anyone else that usually doesn't has permission to access the file.
The generated URL is connected to the user that is sharing the file. If permissions to access the file change for this user, the same will happen to the shared URL.
Functionality will be available with the next PDFE release.