Extract annotation from pdf doesn't work

Hi,

I'm usig Zotero 3.0.11.1 with zotfile extension, Windows 7. I've got strange square lettres in my pdf annotations extracted such as that exemple :

"Les phnomnes de base apparaissent  travers les tmoignages ou les rminiscences qui nous reportent aux ges les plus "

I tried to annotate with Adobe Reader XI and PDF Xchange Viewer and both results are the same...
Have you got an idea about what problem it can be ?
Thanks
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