It is easy to take jeans in at the waist, and there are a lot of tutorials online showing you how to remove the waistband at the back, add a dart and reduce the waistband before stitching it back on .
There are only a few tutorials showing you how to take them in at the hip downwards, so this is how I do it - adding some embroidery at the same time
Start unpicking the side seams carefully from just below the pocket, where there is likely to be some top stitching and finish about four inches above the hem so that we do not have a new hem to cope with.
To hoop the fabric for machine embroidery, your jeans are likely to be in a stretch denim so they need stabilising firmly. I pressed on an iron on stabiliser to the back first, this one is called Totally Stable by Gutterman Iron on stabiliser I also used a layer of Gunold tear away stabiliser and hooped it with the jeans fabric Gunold Stabiliser. Stretch fabrics can be difficult to embroider unless they are held really firmly in the hoop.
This is the design I chose which took twenty minutes to embroider. You can add more embroidery if you like and you could also add some to the back. If you do have some top stitching thread the same colour then you could remove the back pockets, carefully, embroider them and stitch them back on.
This is my finished design . I chose a design in four colours which sits on the thigh . The design would look great repeated just above it.
The whole project took just over an hour from start to finish.
You will have lots of ideas of your own to embelish your jeans. It will certainly give them a new lease of life and they will fit better too.