Not a perfect fix, but if you use the "Logi Options" app for your MX 3, you can add app specific settings for Acrobat, which allows you to customize scroll speed. I'm using Mac Catalina, so some of the steps below may be slightly different depending on your operating system.
App is here: https://www.logitech.com/en-us/product/options
1. Install the app for your OS, open & navigate to "Point & Scroll".
2. Click on top right "All Applications"
3. Toggle "Application Specific Settings" to ON
4. Click "+ Add application"
5. Click on "Adobe Acrobat"
6. Back in the Point & Scroll window, toggle "App specific Point & Scroll settings" to ON
7. Set "Scrolling speed" to the lowest (far left) value
8. Close Logi Options (or just switch to Acrobat) - the setting change should be instant
Optionally, you can turn on rachet mode on the MX3, which also helps slow scroll speed a bit.
Thank you!! I had tried to customize point and scroll, but thought it was locked in global only. Your instructions made me take a second look, and low & behold... SUCCESS! Put speed at 0, smooth scrolling OFF, smartshift off. Works perfectly!