This message when viewing an ebook has no relationship to your NNU print credit. It is giving you that message because the amount of text you are trying to print exceeds the percentage of allowable printing for that particular book. This is governed by copyright restrictions. If you try to print more than half of the book, you are breaking copyright law. If you wish to read the ebook off-line, use the first icon in the top row for downloading the entire book onto a device. This will allow you to read the book off-line without killing any more trees or exceeding copyright.