How to fix a “cannot create directory” error in the DHL Intraship extension for Magento?

This is about the Magento extension called “DHL Intraship“. Here, version 0.1.9 was used in Magento 1.4.2.

An error message appeared like this:

Sendung erstellen
Unable to create directory /var/www/vhosts/example.com/httpdocs/var/intraship/documents/pdf--4/pdf--49/

The solution for this is shown is shown in the Magento forums thread “Sendung erstellen: Unable to create directory var/intraship/pdf–…/pdf–…/“.