I asked my supervisor to post-date mine to May 6th, that + recent paystubs + job contract + T4 I think it should be enough to prove employment AND work experience.
For work experience perhaps include a year’s worth of pay stubs. If they have any doubts they might request additional documents later on but I think that should cover employment.
For students, what I did: scan my diploma + official transcripts + confirmation of graduation + study permit (to prove I had valid status)
On top of that, if you have the chance upload a letter of explanation with your background profile and any additional documents you feel you might need that could help.
I technically don’t need police certificates from anywhere, but I got one from my home country and a RCMP because if they ask later on, that’ll save me weeks of waiting for documents, translating and getting them to review them.
Technically the time to obtain X documents is included in the application time, imagine getting your PR in 4 months instead of 6 because you got everything upfront.