Dated letters from each previous employer stating the position, duties and period, on letterhead and signed by someone who can confirm them, together with the diploma and transcript. Pay records or contracts help where an employer no longer exists.
Experience is proven by employers, not by a résumé
When a profession's rule is diploma plus three years of experience, the experience becomes a document requirement, and a self-written résumé does not satisfy it. Hypothetical example: a Shannon systems analyst's eight years span two employers, one of which was acquired and renamed; she needs a letter from the successor company confirming her dates and duties, or, failing that, T4 slips, contracts and a statutory declaration explaining why the original employer cannot write. Each letter should describe the work in the language of the profession, systems analysis and design, rather than generic IT support.
Alongside the experience evidence, the file carries her passport, the diploma and transcript with certified translations, and the U.S. employer's support letter naming the profession, the credential limb relied on, the duties, the salary and the period. Keep the offer letter and the support letter consistent; an officer who finds different job titles in the two will ask which one is true.