Just republishing from my old discontinued blog on another site…
How to make custom PDFs for your old good Kindle which look like genuine Kindle books?
In MS Word:
Use PMN Caecilia 45 bold, font size 24.
Set vertical line spacing to 1.15.
Export into PDF.
Load PDF onto Kindle device.
On device PDF will look slightly lighter though very very similar to the native Kindle book rendering.