You are integrated with Upflow thanks to your accounting tool? And you are not using the same tool to bill these invoices?
There is a great probability that the invoices imported in Upflow are not the ones your customer received, and they would be confused about getting a different invoice format from you.
This is why we created this simple switch that allows you to hide those 'wrong' invoices from Upflow. You can find it right in your Settings > Invoicing
No PDF will then be available on Upflow.
Neither for your customer on his portal or you on the invoice screen, or in the emails/letters.
Please note that this feature will prevent you from using Upfow to send invoices to your customer.