As of now, We don't have any official update on this!
Any update yet? A year later.
Acrobat Reader for iPhone and iPad does support the following multitasking features on iOS 9 or later.
Please note that Apple iOS supports Split View on iPad Pro, iPad Air 2, or iPad mini 4 only.
Example: Split View with Acrobat Reader for iPhone and iPad (left) and Safari (right)
Additionally, please go to Settings > General > Multitasking and make sure that the "Allow Multiple Apps" option is enabled.