You can do as Miguel said, but if aou have not a lot of resources for translate, you can rename resource description in invoice line.
If you want to use the same functionality as item translation, you can make small customization. I made something similary.
You need to create new table wih fields: Resource No, Language Code and Desription.
After that you need to change invoice report to print resources in other language when customer has it.
Something like that.
