I'v found a few "tutorials" but I just don't "get" how/where they're doing most of the coding well enough to make it work. (e.g. http://inchoo.net/magento/add-gift-message-to-magentos-pdf-packingslip/)
Found this: https://stackoverflow.com/questions/1795725/zend-pdf-word-wrapping but haven't much luck getting it to work. (Actually not sure what to do with this code/where to put it all and have it be available, etc.)
I'm thinking that adding another page to the packing slip or pick slip might work and then including the From/To/Message stuff on that page with some artwork, maybe a fancy font or whatnot will be sufficient. Then, the "extra" page could be slipped into the box by whoever is picking the order.
Not sure at all how to "hack" the packing slip to add a page break and how to work the Zend PDF stuff at all. Any help would be appreciated.