As for off-site shredders - our Provincial government used a contracted company to shred high school achievement examinations. An employee of the shredding company "liberated" a couple of exams and sold them to students. If something is important enough that it should be shredded, do it onsite--do it right.
If you want to be secure, you shred locally, preferably with a crosscut shredder, then burn locally, or have a pulping service come out. They turn the shreds into basically paper mache. As to external services, minimize, scrutinize, and change routines unexpectedly. -- Dave's Engineering Page: http://www.dvanhorn.org Got a need to read Bar codes? http://www.barcodechip.com Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with two or five digit supplemental codes, in an 8 pin chip, with NO external parts.