Opening PDF Invoice on back end.

[joophilverink]

Hi,

When I 'm in back-end orders, and try to open the invoice by clicking the invoice icon, the invoice is not opening but there is an Fatal error:
Fatal error: Call to undefined method JDocumentPDF::addCustomTag() .... plugins/system/productshare/productshare.php on line 87

Is there anyone how can help me out.

VM 2.0.16
J 2.5.6