Prepare to Make Unreal Games with Unreal Engine – Installing and Setting Up - Learning Unreal Engine iOS Game Development - page 13

3D and 2D applications
As this topic will take care of the process of making games using UE4, it is ultimately
down to you whether you choose to use the assets provided with the topic or your own that
will fit your requirements. If you are going to build your own assets, I would recommend
that you use Blender3D for the 3D assets or Inkscape for the 2D assets. I used both of these
applications while I was building the examples presented in this topic. Both are free/open
source applications with high-end quality and tools.