In what app or application and what version?
There is a control in Adobe Reader (computer), Acrobat (computer), and Adobe Mobil Reader (mobile device)?
For Reader and Acrobat one needs to be on the "Recent Files" page and at the bottom of the center panel is the slide switch. For the mobile app you need to be in My Document and on the Recent, Local, or Document Cloud page and it is the top most item in the file list.
It appears to only connect to your account and you must be signed in to the same account of both devices.