dual intent documents

hellooo everybody I'm a French PA to my Canadian common law partner. We have sent in our Outland family class application for PR recently and we are aware of how long the processing times are. That's why I would like to go visit him for a short-ish stay of about 6 weeks to 2 months if we can swing it.

Gathering information is hard so I was wondering if anybody had any insight as to what documents I could show at the border to be accepted in as dual intent. I have a valid ETA from previous trips before the PR application.

Thank you!!