Out of the box DK PDF has support for Polylang multilingual plugin, all you need to do is go to Polylang
Strings translation tab and you’ll see the fields with the strings ready to translate.
I didn’t test other multilanguage plugins but if the plugin you use has settings translation implemented in it, it will not be difficult to deal with this. Anyway if you are in trouble, please create a ticket in the DK PDF support forum.
DK PDF comes with a
languages directory that contain .mo and .mo files from where you can create new language files with a tool like Poedit.