v3.9.11.68 works fine with ios13.
If you are using Revu on a Desktop and in the field, I believe there is value to have Revu on the iPad, but there is also Vu, which is free.
Vu will allow you to do markups in a Session and view .pdf documents in a Project or local to the device, just not edit them.
It's difficult to know what you are looking for from Revu to help you do on the iPad. There are many pdf editors, maybe Revu doesn't provide what you need.