One simple way to fax documents from the database is (assuming you are using Oracle Reports, for example) to send...
an Oracle output to a fax by printing to a printer driver which is set up as a fax driver.
Another solution is to use third-party software such as RightFax.
You can also programatically (using PL/SQL packages) send fax/e-mail from Oracle. Search Metalink and follow the steps in Article 47498.1.