LogicalDOC needs to print documents to a virtual device sometimes when performing barcode recognition.
In general in GhostScript is a package installed by default in all Linux distributions. On Ubuntu you can install in this way
$ sudo apt-get install ghostscript
Once you have GhostScript installed set the command.gs property(in file conf/context.properties) to the path of the gs executable:
command.gs=/usr/bin/gs
For Windows users
In Windows you don't have to do anything since the installer takes car of all installation and configuration issues.