Blender only renders triangles so at render time all faces are triangulated. You either want to make all your faces planar, in complex shapes the effort involved in doing this does not justify the end result, or apply smooth shading to the faces. You can apply smooth shading to selected faces or smooth shade it all and use an edge-split modifier. You can define the sharp edges by the edge angle value or marking selected edges as sharp with Ctrl+E / mark sharp
You can make exactly what you want in blender or any other 3d software. It’s just that you don’t know how. Whatever software you use you’ll always need to learn how to model using it and how to render your image.
ah, I figured out my problem. The issue was the conversion into Pepakura Designer. I finally found someone else who had the same issue. They just exported the file from Blender as an *.obj as opposed to a *.3ds and the faces were flattened for me.