The Aviva pants are a made to measure and size inclusive pattern, this means you measure yourself and then follow the instructions. Therefore, they can be made for any size and age. I used roughly 1200m of 6ply (sport weight) cotton yarn for the sample size which is a small (UK 8).
The pattern is written in US terminology and is an advanced beginner level.
English only, however there are pictures throughout each step and a stitch graph for the diamond stitch.