Um, I do not understand why Seoul Metro does not update English version of Seoul subway map. I tried get New version of Seoul subway map of English, Chinese and Japanese, but I could not find yet.
So I took picture at Hongik Univ Station, I will link Map image file.
This image is not easy to read at once, so you need at least image view program.
This is a update version of Seoul Subway Map of Korean and English.
Also AREX Line and KyungChun Line are included.
The latest Seoul Subway Map (PDF File) can be downloaded here.