Print-on-demand (POD) services are available from two quite different types of POD vendor - POD publishers and POD printers. It is important to understand the differences. POD Publishers, as the name suggests, act as the publisher of an author's book and pay royalties on any copies sold. They also provide ISBNs and bar codes, and various services such as undertaking some of the work involved in publishing a book. Remember that the POD publisher will register the ISBN as and hence become the publisher of record.
When a POD printer is used, the author becomes the publisher of his or her own book and has much more control over what happens to it. The POD printer just prints whatever is submitted in return for the appropriate payment. Author must purchase and register a block of ISBN number from the appropriate ISBN agency and can then allocate numbers to their own books. Bar codes are obtained by authors as a separate exercise. To obtain a block of ISBN numbers is is necessary to provide details of the publishing organization which, as a minimum, might be a home address and publishing company name.