The PDF file is the french version of the original pattern which is available for free on KNITTY.COM
From the pattern website:
I wanted to create a half and half sock with semi-solid and self-striping yarn. But equal halves was too boring. I came to work this pattern with “waves” of colourways and the STITCH SURFER was born!
You will notice that there is no “right” and “left” foot on this pattern. This pair of socks can be worn either way: with the solid color MC in the middle or on the sides. You will obtain a ripple at the junction of your foot one way or the other!