What if I need to provide my client or printer with original source files?

You are allowed to provide your printer with source files for the sole purpose of printing your work, provided that once the printing has occurred, the supplied files are deleted from their system. 

You are not permitted to provide a layered file to clients. Instead they should be provided with the final, flattened designs. If your client requires access to source files to make additional changes to the design, including the a vector file for a logo, for example, they will require a license of the graphic/font for themselves.