If sometimes on the back office of your shop you don't have the button "Load and Modify the Project" for edit the project of your customer on him order, you can do that by an another way.
1. Open on new tab when you click on "Download PDF File" on this tab look the url at the top something like that :
This part "fb50f378f771dac5f4d2fb123cec20cd" is the id of your project.
2. On the same or a new tab enter this link : https://pitchprint.net/admin/editor/edit-project/?p=(and here past the id of your project without)&u=2