I just wanted to add that pressing the control key and starting reader did not work for me. The language would not change that way. So I did the following and finally got the language to change and I could have picked from any language in the list ... but English is the only one I know besides French so... hope this helps anyone who was not successful with the control key method. Hope I don't offend anyone.
1. In Russian the spelling of the word "Language" is "Язык"
2. Open Adobe Acrobat and you will see the Russian language.
3. Go to the Edit Menu, the second drop down or look for "Редактировать"
4. Go down to the bottom selection "Предпочтения" which is Preferences.
5. In the panel find "Язык", which is the "Language" selection.
6. in the right side, first drop down you will see 3 selections ..Russian, Choose at Application Startup and Same as The Operating System (I translated in Google). Pick one of the other 2 (one at a time if necessary) and hit OK at the bottom of the panel each time. This will cause Acrobat to ask for a language next time you start it or use the operating system language.
7. Note that I don't know which of the 2 selections worked as I did both before I restarted the app Cause I was guessing at first. But I now have English as my language and I could have selected from many others.