SDcard in lollipop still readonly using EZPDF
Although the new Lollipop update allows apps to write to SD Card, it requires the user to grant the apps access, like you've stated above.

For apps to gain access they have to call the new API introduce in the   lollipop which allows user to grant app permissions.For the apps to call this API, the devloper of the apps have to write code into their app to do this.

As I was saying above, the devloper needs to write some code to do this, for which the particular app you want to grant the access SD Card does not have.

I am sure that their are ways to forceable do this, of which I don't know of, that would probably require root, phone modification and technical know how to do.