This cute chunky looking cardigan is made using a simple hdc (htc UK) stitch and bobble stitch for the body, it is quick and easy to work up.

The PDF is 30 pages with each size written separately.

Sizes
Preemie to fit 13 inch chest
Newborn to fit 14 inch chest
0-3 Months to fit 16 inch chest
3-6 Months to fit 18 inch chest
6-12 Months to fit 20 inch chest
1-2 Years to fit 22 inch chest
3-4 Years to fit 24 inch chest
5-6 Years to fit 26 inch chest
7-8 Years to fit 28 inch chest
9-10 Years to fit 30 inch chest

Materials
Approx 200 / 250 / 300 / 350 / 420 / 520 / 640 / 750 / 890 / 1050 meters of dk / 8ply / light worsted yarn
4 mm hook
3-6 x 15-25 mm buttons

Written in English US terms with abbreviations for UK terms

Gauge Square
With 4mm hook
Row 1: Ch11, hdc in 3rd ch from hook and each chain across. (9) Turn
Row 2-5: ch1, hdc in base of ch1, hdc 8. (9) Turn

Square should measure 2 inches x 2 inches.
If you’re out with a 4mm hook try a 4.5mm hook.
If you have problems hitting the length but the width is ok, try dc instead of hdc.