Adding XPM Web site extension to the existing staging Web site. As per SDL Tridion reference guide it ask to add content placed in cd_preview_web.war to the staging website. This cd_preview_web.war contain 64 jars in lib folder. Do we need to add all these jars to staging website or there is a specific list of mandatory Jars.
Yes, you need to add all those JARs to the website. If you completely follow the instructions then you might remove some according to your environment (i.e. which web server you are using).
If you're currently using the Content Delivery API in your site then you probably have most of them already added. Depending on what functionality you use then I guess you might not need all of the JARs, but there's no reference as to what's needed for what functionality/connectivity and if you ever have issues and need to work with SDL support then probably one of the the first things they'll ask you to do is confirm that all of the JARs are in place as specified in the documentation.