Some Notaries misguidedly keep copies of every document they notarize. They shouldn’t. Many documents contain sensitive information about signers, which increases liability should that information ever be compromised. Also, documents such as mortgage and real estate contracts easily can run hundreds of pages.
There is one exception to this practice. Some states permit Notaries to certify a copy of a document. If your state does, it’s advisable to keep a copy for your records because you are certifying its completeness and accuracy. Otherwise, everything you need will be in your journal.