That's a too simplistic answer.... nope...
If they become suspicious or whatever reason.. they could ask you to furnish with all your paystubs.... they wanna see if you worked as a part time or full time.. in order to make sure that you have one full year equivalent of work experience.... In the preliminary application step, you will be sending your application forms with supporting document to "Central Intake Office". In this step, you will not required to submit employment experience letter, but you do have to mention (claim) NOC code for each occupation of your work experience and responsibilities..
Why don't you read the guide at least three time, then start asking questions here...
http://www.cic.gc.ca/english/pdf/kits/guides/EG7.pdf