wkhtmltopdf Log in to asp.net web app

First, check the login form what post parameter it uses then try --post username xxx --post password xxx. Alternatively use wireshark and record the login process and see what parameters were posted.

Once u are logged in use --cookie-jar

See a better explanation here http://wkhtmltopdf.org/

getting wkhtmltopdf to convert a protected page can be tricky. Use also --extended-help to see other parameters u can use to login. e.g. if the site is protected by basic authentication it should be fairly easy with --user --password