A Canadian passport, the original employer letter describing an Engineer position with duties, salary and duration, his degree and transcripts, a résumé consistent with the letter, and any credential evaluation if the degree is foreign. Bring originals and a set of copies, and retain a complete copy of everything submitted.
One consistent set of originals, read in the officer's order
The port-of-entry application is decided from the documents on the counter, so the set has to be complete and internally consistent. The passport proves Canadian citizenship, which is the threshold. The employer's letter carries the case: it should identify the employer, state that the position is an Engineer position, describe the engineering duties in concrete terms, give the salary, state the intended period of up to three years and confirm the stay is temporary.
The degree and transcripts show the qualification; if the degree is from outside the three USMCA countries, a credential evaluation from a recognized service is required. The résumé should use the same job titles and dates as the letter, because the officer may compare them. Where the engineer has previously been refused, or where the employment runs through a staffing arrangement, a short cover explanation is useful, but a case that needs several pages of explanation is one the petition route handles better.
Bring originals and copies; the officer may retain submitted supporting materials, so the applicant should keep a complete copy.