In Akti, it is possible to add files to your invoices. Therefore you have to check the settings of the Invoicing module.
Before you can add files to invoices, the Dropbox integration needs to be activated first.Go to 
Settings invoices and choose "Attach files" in the basic settings. Click on "Upload" to select the files in Dropbox. Finally, do not forget to tick this file if you want to send it as a standard attachment with your invoices to the customer.
Via 
, you can delete already uploaded files afterwards.