I've made some patch to include direct printing of faxs capability to the fax module.
First you need to install cups to your server. ( yum install cups )
And define a printer via the cups web interface yourserver:631
Name you printer ex myprinter
From the file attach replace :
faxrcvd-elastix.php in /var/spool/hylafax/etc
faxlist directory from /var/www/html/modules/faxlist
faxnew directory from /var/www/html/modules/faxnew
fax.db from /var/www/db, or only add a row printer in the fax.db
In the Elastix web interface add a new fax and in printer input field put the name of your printer ( myprinter )
And that all, when you send a fax it is print automatically.