Thanks for your request. We have made a note of the same and shall try to incorporate it in one of our future releases.
I was surprised to see that this feature is not included already.
I bought bluetooth mouse for my Lenovo Tab 2 A7-10F and now it is difficult to use it without scroll wheel.
More than one year can not find any update of it.
Dropbox pdf viewer works with a scroll wheel in Android. Convenient for not having to lift your arm.