look i struggled a lot about this, researched, talked to a lot of people. no definitive answer. at the end i decided it doesnt make sense to give letter for each job experience. it would be too much for me to collect, and too much for cic case officer to verify. you get top points if you claim 3 years of experience. so at the end i entered only last 2 jobs over 4 years to the work experience section.
there is a personal history section, i entered there all the job details.
then it gives you the documents required, the system only asked for the 2 jobs i claimed points for.
this is what i did based on logic, no guarrantees its right, but this is what makes sense both for applicants and cic case officer.
hope it helps.
