Will I see performance boost if I add memory with these Page-In/Page-Out statistics? Currently, if I open Photoshop after a days time, the load up time is about 5 seconds.  If I close and open again (right after), the load up time is about 2 seconds (I assume this is caching?).  Can someone explain how adding memory will (if at all) increase performance here (4GB to 16GB)?  

Background Info: My Page-Ins are about 2GB and my Page-Outs are about 60MB (iMac 12,2 4GB RAM).
The increase speed you see when starting Photoshop immediately after previously starting and stopping it is coming from the hard disk cache which cannot be increased, and adding more system memory will not make much difference unless your allocated memory is sufficiently high to require significant paging out to make room for the new app.  As any paging will have taken place on the first load, it's unlikely to require more paging on the 2nd attempt unless you re-access the data that has been paged out so that is get's paged back in, which you do not allow time for in this scenario.  Your page in/out figures need to be better detailed to allow for proper consideration - how long is this sampled over etc?