Don't bother!
Adobe Acrobat Reader is resource-hungry, incredibly slow to open large pdf documents and a backdoor for hackers to gain access to your computer.
The most popular (and vastly superior) alternative is Foxit
https://www.foxitsoftware.com/products/pdf-reader/
Using an older version of Acrobat Reader will leave your computer open to attack from hackers but, if you really insist upon doing it, uninstall the present version, then download and install an older version from here:
http://www.oldapps.com/adobe_reader.php