problem to generate pdf of node

when I try to get the tex source or the pdf for a node, I get nothing (the file doesn't exist).
The tex display correctly.
I have a lot of notices:
Notice: Trying to get property of non-object in drutex_node2pdf() (line 155 of /var/www/sites/all/modules/drutex/drutex_pdf.inc).
Notice: Use of undefined constant filter - assumed 'filter' in preg_replace() (line 1 of /var/www/sites/all/modules/drutex/drutex.module(363) : regexp code).
Notice: Undefined index: en in drutex_node_view() (line 81 of /var/www/sites/all/modules/drutex/drutex.module).

In the system log there is only that the file (node.pdf e.g. 5.pdf) doesn't exist.