Evidence of Canadian citizenship, an employer letter describing prearranged employment and the technical duties, a statement from or about the supporting professional identifying their discipline, and records of the education and training that establish theoretical knowledge.
Build the file around the technical relationship
Start with the two documents nobody else can supply: proof of citizenship and the professional's description of how the work supports their own. Then add the employer letter, which should describe the position, its duration, the arrangements for payment and where the work is performed. For the knowledge requirement, gather transcripts, technical certificates, records of method training and, where available, a summary of the standards and analytical procedures you routinely apply.
Avoid padding the file with generic employment references. What helps is material that shows the technical substance of the role; what does not is a stack of letters attesting in general terms that you are hard-working and reliable. The strongest files here are short and technical rather than long and complimentary.
Hypothetical example: Mateo tests corrosion coupons for a pipeline-coatings supplier. The initial document review should produce a short evidence map: citizenship proof, an employment description, the named scientist's account of the support work, and records showing what Mateo understands and applies. A calibration log may establish technical responsibility better than a generic reference.
Request the professional's statement before the employer finalizes its letter so the two documents use compatible facts. Files falter when certificates are supplied without explaining their technical content, or when the professional is mentioned only after the duties have been written as ordinary production work.