Lol, I actually do that will all my files. I don't have papers anymore but I have invoices and SOWs and more and they all include my full name and date. I just realized I am that thoughtful, although it's mostly due to me being incredibly annoyed when I get another invoice.pdf and it lives in my downloads folder and then I have to open it later to figure out where it came from.
I enjoy making the envelopes, and seeing the poor post office workers face when she sees them. They're usually all different colors (lil sent me a pack of awesome pens that I always use) and have silly drawings and writings. I decided to tone it down a bit this time because the post office worker told me they might get returned last time.
Some did end up getting returned but I still think it was due to them being over 1oz, not the amazing drawings and messages. :P