Hi,
when choosing the category for a topic please try to have a look at the category description for each category first:
The current used category is/was Greenbone Professional Edition - Greenbone Community Forum (Description: About the Greenbone Community Edition (GCE) VM) which is about the Greenbone Community Edition virtual machine provided by Greenbone directly. You are using packages for CentOS which aren’t provided by Greenbone therefore you are talking about the Greenbone Source Edition.
First of all you are using an old and unsupported version of OpenVAS/GVM. Current stable is GVM 10.
gvm-tools does not support this version of OpenVAS too despite it may work for many GMP commands. Additionally you should search in this forum for PDF creating issues and howto setup your distribution for this purpose. There have been several topics about this problem.