If a user is getting this error when trying to print a subcontract:
Follow these steps to find the invalid characters and delete them:
You can check the characters by clicking the Project Name at the top of the treeview on the left, then clicking the 'Edit' button. If invalid characters are entered they'll show up as these question mark characters as show here:
Then you can go to Maintain Business Partners on the Enterprise tab and pull up the customer and look for any empty fields in the Address tab or extra space at the end of the fields and delete the spaces if you see any, then click save.
After making the changes you can go back in to the Field tab to see if the question mark characters are now removed.