pdm and pdm-backand are two different products, even though they related one to another closely.
It was very confusing to me that during reading pdm documentation I have found myself in pdm-backend one without noticing.
The problem is, both sides are using almost identical theme.
Proposed solution: use different themes
Change the theme for pdm-backend somehow, e.g. to different color.
It would contribute to more intuitive understanding that pdm differs from pdm-backend and what documentation is currently read.