Impacted versions: ODOO 10

Problem.
If i print a invoice with a negative amount, the pdf shows a vertical bar instead of a minus symbol.
![image](https://cloud.githubusercontent.com/assets/28800797/26237253/b07fadb0-3c74-11e7-86c2-c8688d82b5a5.png)

I have tried to install a new pdf reader, but with no result.
openerp/addons/test_converter/tests/test_html.py
_model = 'test_converter.test_model'
class TestCharExport(TestBasicExport):
    def test_char(self):
        converter = self.get_converter('char')
        value = converter('foo')
        self.assertEqual(value, 'foo')
        value = converter("foo<bar>")
        self.assertEqual(value, "foo&lt;bar&gt;")
class TestIntegerExport(TestBasicExport):