Could not acheive to do the job

I've installed the module and enabled it.
Under site/all/libraries i've copied the related "mpdfXX Lib" in a "mpdf" directory.
such as site/all/libraries/mpdf contains the downloaded library tree (I.E /classes, / includes, /mpdfi...)

All i see now, is two new views, one for line-item and one for orders with their name in relation to that module.

For the moment , i havent configued those views to set my specific informations or change anything to display.

On the view default "user list of orders", i ve added a "download pdf order" field in the table.

When i display the view of the user list of order and click on the download link, i ve a error :
"Fatal error: Class 'mPDF' not found in " a path related to the commerce_order2pdf.module

How can i ensure that the mpdf library is correctly installed ?
Does the link must be somewhere else, is there another thing to do ?

Thx