Hi
i have got wkhtmltopdf installed and working but i don´t know why odoo don´t find it
$ 2016-08-11 06:34:12,635 943 INFO odoo8l2 openerp.addons.report.models.report: You need Wkhtmltopdf to print a pdf version of the reports.
i downloaded in http://wkhtmltopdf.org/downloads.html