The error message indicates you have exceeded the percentage of allowable printing for that particular book. This is governed by copyright restrictions and has no relationship to your NNU print credit.
If you wish to read the ebook off-line, you may download the entire book onto a device. This will allow you to read the book off-line.
For EBSCO ebooks: Click "save pages" and save as a PDF
For ebrary/Ebook Central, follow these instructions: http://support.ebrary.com/kb/download-entire-e-book/