This section lists questions frequently asked about ISBN and ISMN identifiers. For instructions on how to use the service, please refer to the section entitled Instructions.
You will need two identifiers. If the publication appears simultaneously in print and online, both identifiers must appear in both versions. All different file formats of the publication are assigned separate ISBN identifiers, and a note of the format will be added to each ISBN.
ISBN xxx-xxx-xx-xxxx-x (paperback)
ISBN xxx-xxx-xx-xxxx-x (PDF)