http://www.ghacks.net/2012/03/14/nitro-pdf-reader-2-3-improves-memory-usage/
Nitro PDF Reader 2.3 Improves Memory Usage
Windows users have plenty of options when it comes to pdf readers. From Adobe’s official Reader application, to built-in reader support in the Chrome browser, or the bare-bones Sumatra PDF
If you do not want to pay for a product like Adobe Acrobat, you could try a free alternative like Nitro Reader. While not offering the same feature set as commercial alternatives, it comes with options that many free readers do not come with.
The developers of Nitro PDF have just released a new version of the program. Nitro PDF Reader 2.3.1.1, available as a 32-bit and 64-bit program for the Windows operating system