A Canadian passport, the employer's letter, the degree parchment and transcript, and anything that proves the credential is what the profession entry asks for. Everything should be organised so a single officer can follow it quickly.
Build the file so the argument is visible in the first minute
Hypothetical example: Put the employer letter first. It should name the company, the position, the professional duties, the salary, the temporary period of employment and the location of the work. Behind it place the degree parchment and the transcript, then the passport.
If the degree was earned outside Canada, Mexico or the United States, a reliable foreign credential evaluation belongs immediately after the parchment, because without it an officer cannot verify that the degree is equivalent. Add a one-page summary if the file is thick, naming the Appendix 2 entry being relied on. A Canadian citizen may present this at a land border, at preclearance or at a port of entry, and no visa stamp is issued.
Alternatively the employer may file Form I-129 in advance, which produces an approval notice to carry instead. Filing charges appear in the USCIS fee schedule.