Vector Outline Outside at some curve angles looks low resolution (sort of too polygonal). Setting document to higher DPI can't fix this problem. Problem remains if rasterize or flatten image.
Guess this happens due some sort of too strong simplification of vector points used to build outline (probably to improve speed and performance).
I checked some other apps and they don't have this problem if use special "smooth" or "round" interpolation modes. It is also interesting that exported PDF previewed in macOS looks smooth compare to PhotoLine view.
PhotoLine:
Other apps:
PhotoLine vs macOS PDF preview:
