Introducing the plugin Short pixel image optimiser
https://wordpress.org/plugins/shortpixel-image-opt...
Short pixel image optimiser is what I would call a freemium plugin for WordPress.
There is a free version that allows you to compress 100 images per month or you can purchase a premium package. I suggest the $10 for 10,000 images. or 1 cent for 10 images compressed, pennies!
Short pixel image optimiser is as it suggests a lossless image optimiser. What I like about it is that I could just install it and have it optimise all of my previously uploaded images often referred to as "bulk optimisation".
When you have this plugin it, it works away in the background compressing your images and their thumbnails automatically without you having to do anything, truly a set and forget plugin.
All you have to do is install the plugin and activate it. for WA hosted sites, you may need to contact support with a screenshot, and they will fix and impeding technicalities for you in an instant.As you can see from the image above short pixel will also compress any PDF that you have on your wordpress site.