I can't find a way to protect the list of jobs listed in 6700DN web interface.
Anyone can access the list and delete the job records list.
I already blocked all web pages from options, access rights, web pages access but jobs tab is still available for anyone.
If you are concerned about security, then you could send the jobs as Secure Print jobs, which would require a password to release (print), but would prevent users from logging in and deleting jobs.
If you're not concerned about security, but rather just an individual user is making things difficult for you, you could use IP filtering to block all use of CWIS from specific users.
You can read more about IP Filtering in the System Administrator Guide here: http://download.support.xerox.com/pub/docs/6700/userdocs/any-os/en_GB/sys_admin_guide_en-us.pdf (Pages 47 & 48 specifically).
If you don’t want to completely block CWIS, or use Secure Print however, there are no other alternatives for you with this model of printer unfortunately.
Recommendation is from our Second Level Support. If you require more detail or assistance you may contact them at 1-800-835-6100.