You can also set up image quality to 80-90% - this should make the file size smaller, but images would still look very sharp.
Compressing smaller images has little effect over the overall document size.
The process takes a few seconds to a couple of minutes, depending on the file size.
There's no need to download any kind of software.
Amazing compression without losing quality.
At times, it is necessary to compress these files to be able to send them as email attachments or upload them to websites.