I use Reader on both Windows and Android. However, on Android I miss the Alt-LeftArrow that would take me back after I tap a link. Studying a more involved document, in my case a math textbook, would be much easier with it. I was hoping the left triangle would work, but it just ends the application.
Once you switch to the another page, you can tap on the page number indicator(small triangle showing the page number). This will open the Go To page dialog from where you can go to the previously viewed page. More information about the same can be found here: Acrobat Reader Help for Android: Navigation. Please let us know if you still observe any issues.
Adobe Acrobat Team