It'd be nice to be able to have a fulfillment plan that automatically prints a PDF file attached to an order of a certain name. This could be used to have fully customizable packing slips, or I imagine it might be useful in other situations.
This should be possible! First, we have a feature called 'Smart Documents' (linked below) that allows you to create your own custom PDFs based on information in the system. Once a smart document is created, it can be added to a fulfillment plan so that those documents get generated with your other pick and pack docs.
We also have the ability to use the API to get and attach files. We have one client in particular who uploads a document to every item receipt (regarding quality assurance information for those items). They then use a script to go and grab those files anytime the receipt is allocated to an order. Once it has the files, it attaches them to the order and they become available in the ship station UI.
Hope this helps!!