We had an issue on an Exchange 2010 multi role server this week where the average Memory Pages/Second exceeded 3000. Microsoft recommends that the average Pages/Second should be below 1000.
After some investigation we found that the antivirus software was scanning the Exchange folders and log files. For a quick test we disabled the antivirus agent on the server and the average Pages/Second dropped significantly. There could be countless reasons for above normal Memory Pages/Second issues but checking your antivirus software is a quick check.
The exclusions in the antivirus software was then configured and the issue was permanently resolved. Note that you should never scan your Exchange log files or databases. Check the Microsoft Technet site for exclusions on the Exchange version that you are running.