How can you ensure security of your clients’ tax return information?

As tax preparers, we are responsible for maintaining privacy of all tax return information in accordance with IRS privacy code, Section 7216.  Most tax preparation software encrypts the clients’ date when e-filing.  However, if you save your clients’ tax returns as PDF files and e-mail them to the client, how can you be sure the PDF does not get into the wrong hands?   How can you ensure that your employees do not take client information out of the office, including clients’ names and addresses?  Do your employees sign an employment agreement that includes a provision requiring them to adhere to IRS Section 7216?  How can you keep employees from leaving taxpayer documents in view where unauthorized persons might see them?  Do you adequately cover security of clients’ tax return information in your employee training?  What are the best practices?