Mi auto-rispondo. Lavorando su windows la documentazione è scarsa. Dovrò passare su ubuntu.
Comunque ho trovato la soluzione che riporto:
www.odoo.com/it_IT/forum/help-1/question...-shown-in-html-69759
Abdullah Sofan
On 08/12/14 14:30
This is for Windows:
First, download and install wkhtmltopdf for your version of windows (32 bit or 64 bit).
Once it's installed, go to Openerp/odoo and go to Settings> Users and click on your user
Click edit and scroll down and look for "Technical Features" is enabled / checked.
Click Apply, then log out of Odoo and then login
Go to Settings again and now you should see several new technical menu items on the left
Go to Settings -> Customization -> Parameters -> System Parameters
Click Add and for Key insert : webkit_path
For value insert: C:\Progra~1\wkhtmltopdf\bin\wkhtmltopdf.exe
Apply and exit and restart Windows.
After you do the above steps, go to System in Control Panel.
Click on Advanced Settings. The System Properties window will pop up.
In the "Advanced" Tab, Click on "Environment Variables".
In the "System variables", scroll down until you find the "Path" variable and double click. !!!!!NOT user variables
inside the "Variable value" field, add this to the end: ;C:\Program Files\wkhtmltopdf\bin
Click OK and then reboot your system.
I hope this helps.