Is that possible to trigger "Print PDF to Devonthink Pro" service by KM shortcuts instead of using cmd+P and choose this from menu?

[Blanc]

I’m not sure if this is what you mean, but you can set up a global shortcut in macOS to print PDF to DT; I’ve set up command-P for that too, so if I want to print to DT I do command-P command-P. KM could do the same, presumably.