Many marketing communications projects involve the use of content from a variety of sources: photos from a commercial photographer or stock agency, diagrams from an illustrator, text from a freelance writer or other paid contributor. In your role as a marketing communicator, it is vital to understand the many legal requirements for using these content elements.
My book Copywriting That Sells High Tech presents a summary of legal issues such as copyright, work for hire, and usage permissions.
A more extensive explanation is provided by the book Fair Use, Free Use and Use by Permission, by Lee Wilson.
Clearly written by an intellectual property attorney, the book discusses many of the issues and scenarios you'll commonly face in publishing content. Particularly useful are the checklists, information resources, and sample permission letters contained in the appendices.
If your work involves the use of any externally generated content, you'll want this book on your shelf.