Hello I installed web_pdf_viewer in Odoo 9. It is giving above error when trying to Print SO/Invoice/PO

Odoo Client Error

Uncaught SyntaxError: Unexpected token T in JSON at position 162

http://localhost:8069/web?debug#id=6&view_type=form&model=purchase.order&menu_id=238&action=310:7Traceback: SyntaxError: Unexpected token T in JSON at position 162 at JSON.parse (<anonymous>) at HTMLIFrameElement.<anonymous> (http://localhost:8069/web/static/src/js/framework/ajax.js:228:40) at HTMLIFrameElement.dispatch (http://localhost:8069/web/static/lib/jquery/jquery.js:4641:58) at HTMLIFrameElement.elemData.handle (http://localhost:8069/web/static/lib/jquery/jquery.js:4309:63)

Please help