Thank you so much dear .There is nothing like CAN+ visa. When you apply for a Canadian visa, the system ask you questions regarding your old US/Canada visa and flag your application as "CAN+".
Its only a flag on the application that "this person have/had a USA or Canada visa and traveled previously". This flag May or May not be used by the officer to assess your application.
I have seen refusals even when they were CAN+ applications
I have seen approvals without any CAN+ application
So, just apply the application and be hopeful.
what are the main/Important documents to upload please advice.