Adding RAM will only improve performance if all of the existing RAM is being used (when all of the existing RAM is used, swapping to and from the page file occurs).
In your case, the page file should be on the SSD anyhow and so any degradation in performance due to swapping would be lessened (due to the high speed of the SSD).
If you are only using Office type applications, it would be unusual to need huge amounts of memory. Your reading of memory usage in Task Manager supports this.
You should never disable the page file (it can cause system instability).
In any event if you are only running Office type applications you should not need high performance.
Replacing CPU might improve things - depends, amongst other things, what motherboard you have. But I count it will make a huge difference.