Some vendors/publishers allow printing (or emailing) of parts of an ebook. The chart on the main E-book FAQs page details specifics about what users are allowed to do with e-books from particular vendors/publishers.
Many UNR library ebooks cannot be downloaded onto an ebook reader or desktop computer.
Some publishers will allow you download sections of a book as a PDF, and many ebook readers will allow you to view/load PDFs onto them.
EBook Central (formerly called EBL) and Ebsco books can be downloaded onto ebook readers that are compatible with Adobe Digital Editions. (Note that Kindle devices are not compatible with Adobe Digital Editions.The Adobe website maintains a list of supported devices: http://blogs.adobe.com/digitalpublishing/supported-devices.) Springer ebooks can be downloaded as PDFs and loaded on any device.