There is no explicit article stating multi-tenancy is not supported for Pega Marketing but please be assured that the product does not currently support it. We were informed about a misleading note in the Pega Marketing Implementation Guide which might indicate the support is there but we have corrected it. The document error was caused to due the usage of standard document templates.
Would you be able to explain why this capability is being asked for and is there a business requirement for this? If yes then please share it us and I can get the Product Management to review and respond.