The employment agreement, a letter describing each placement and its duration, the state licence, the degree and transcript, and proof of Canadian citizenship.
Explain the structure before the officer has to reconstruct it
A file for a multi-site assignment should open with a short written explanation of the arrangement: the employer's name, the fact that the therapist is its employee, the client facilities where services will be delivered, who supervises, and the expected duration of the engagement. Behind that put the employment agreement itself, then the employer's letter setting out professional duties, salary and the temporary period. The state occupational therapy licence follows, then the degree parchment and official transcript, then the passport.
Where a degree was earned outside Canada, Mexico or the United States, include a reliable credential evaluation. Keep the whole thing indexed and short. An officer confronted with a stack of unlabelled contracts will ask questions to build the picture, and answering those questions under pressure is exactly the situation a well-ordered file avoids.