No need to use Keyboard Maestro or Applescript. You can automate it entirely from inside DT on Mac.
Add your Instapaper’s RSS feed to DT, and then set a smart rule to automatically move each PDF to the desired location.
I’ve got mine set up with Raindrop.io’s RSS, but it should work the same with Instapaper.
Two screenshots below.
- The first shows the DT RSS settings.
- The second shows the DT smart rule.