I have a 2013 HP Envy dv7 with Win8 pre-installed, upgraded to Win8.1. I shrank the windows partition by 100MB and made two new partitions for Ubuntu (root + home - 80MB on /dev/sda7, swap - 20MB on /dev/sda8). I basically followed these instructions:
including the boot-repair steps on linux and Windows. Secure boot is disabled.