Short of getting a new laptop, adding more RAM is probably your best option; it will expand your gaming options considerably. The A10 APU doesn't disqualify the Lenovo from playing games, but it is clearly designed for general productivity and efficiency.
You could try running Batman with your current specs - the recommendations you see on Steam and elsewhere are often designed to "cover the studio's back". Even if you get a warning that some of your specs are too low, most games will actually work. You may have to settle for medium settings instead of high or adjust the resolution.
The problem in this particular case is that Batman: Arkham Knight is very heavy on graphics, and even with an extra 4GBs of RAM I doubt you'll be able to play it to any enjoyable degree on the A10.
Sorry,
GreyCatz.