Memory Pressure is a better indicator of the health of the virtual memory system than the traditional UNIX measure of free, inactive and active pages.
For a brush up on the previous measure, have a read at:
Now, the caching of files is drawn as a good thing (green memory pressure) and you will only see the pressure raise in the main window of Activity Monitor when you have a large proportion of wired memory or the system starts swapping RAM to storage and evicting too many cache pages.
The image from your window looks perfectly fine - so I wouldn't worry about reducing the pressure. If you want to reduce the pressure, you can do so by quitting apps and then letting the system manage that memory. If your Mac can accommodate more RAM, adding RAM would reduce the pressure for the same line up of programs running and using memory.