You mean Offer Letter ?
Well Letter I am using is the one my company have filed for Work Permit extension.
So, It says salary, job description, full time, etc.
I am not sure how does the WP extension letter looks like maybe I can refer you to senior members @scylla @DelPiero07 @jes_ON to review and comment on.
with that being said, include your pay stubs(6 months), T4(redact your sin#) as well.