The limits are due to the terms of licensing and copyright, so that they're not just giving books away. The usual limit on eBrary is 60 pages per day per text. If you need more, you may have to do a daily batch for a few days. So it's a good idea to view the text online before choosing which pages are essential to download.
Another alternative within eBrary is to “borrow” offline access to the entire text for a limited amount of time. So try that, if it's a better fit for your needs.