Hi AswinPutra ,
Thank you very much for your reply.
As mentioned above, there are no known issues or bugs. I am not sure what is a purchase order invoice pdf, but I think you may be referring to the actual purchase order pdf that generates after you click the pdf icon? This feature works fine and has no issues. In case your site does not work as expected, pls, open a support ticket. The issue will be in your site, not ATUM, but we are willing to help you anyway.
Multi-Inventory has nothing to do with automatic emailing, nor with any pdf. Auto emails for POs will be introduced late 2019 in our premium Purchasing addon.
Hope this helps.