Empty Memory Computer System Without Rebooting

I do document conversions. I work with MS Word files anywhere from 6MB to 23MB in size. If I reboot the computer and start a processing task I get no hangs. However, the longer I work on a task like a "find and replace", the slower the computer's processing gets and then I run out of virtual memory. When run out of virtual memory, I can no longer save the file.

Is there a way to reset or empty out the memory of my computer system without rebooting the system? I can copy and paste a small amount of text like a comma, but that does not help the memory problem. Edited to correct spelling error.