Due to a limitation in PHP you may find the translations of the "Paid" and "Unpaid" text on the PDF Invoices do not display upper-case accented characters correctly. The problem here is that the native PHP uppercase conversion functions cannot convert special characters into their upper-case equivalents.
There are 2 solutions :
1. Edit the language file to contain the uppercase version of the status text by default for invoices. ie. Change "Non payée" to "NON PAYÉE"
2. Make the following template change in the invoicepdf.tpl file:
For this second solution to work the MB String functions library needs to be compiled into the PHP build on your server (http://uk.php.net/mbstring).