If you want to reject a submission before putting it through review, use the "Archive" link on the submission's Summary page. Depending on the version of OJS you're using, you'll be asked whether you want to compose an "Unsuitable Submission" email to the author; if you like, you can skip the email.
Public Knowledge Project Team
Don't miss the First International PKP Scholarly Publishing Conference
July 11 - 13, 2007, Vancouver, BC, Canada