I found this class which enables you to digitally sign PDF.
I downloaded it and also Zend classes. Install openssl to my webserver.

The problem is that it shows errors with file paths.
my file directory looks like this
and the rest of downloaded files in the same directory

The first error look like this:
Warning: require_once(Zend/Pdf/Page.php): failed to open stream: No such file or directory in /home/www/mvavra/devel/office_wtime/include/pdf/Zend/Pdf.php on line 27 Fatal error: require_once(): Failed opening required 'Zend/Pdf/Page.php' (include_path='.:/usr/lib/php5/php') in /home/www/mvavra/devel/office_wtime/include/pdf/Zend/Pdf.php on line 27

If i repair the path to Pdf/Page.php, the this error is gone but another path error shows then.

I dont use Zend framework so I am not sure if the directory path is correct.

Can anyone help with this?

The require statements in Zend Framework are relative to the Zend directory. You therefore need to add Zend Framework to your include path:

set_include_path(implode(PATH_SEPARATOR, array(