Unable to Download Nessus Scan Report as a PDF Report File

If you are not able to export the nessus report as a PDF Report file than then there might be few of the Issues listed below.

1. Your version of Java does not match the version of your operating system.  You need the 32-bit version of Java for 32-bit operating systems or the 64-bit version of Java for 64-bit operating systems. 
   
   
2. Oracle Java or OpenJDK was installed after the installation of Nessus.
   
   
3. Oracle Java or OpenJDK was not installed in its default setup folder.

Resolution

1. Reinstall the correct version of Oracle Java or OpenJDK, and then restart the Nessus service.
2. If you installed Oracle Java or OpenJDK after you installed Nessus, restart the Nessus service.
3. If Oracle Java or OpenJDK was not installed in its default setup folder, use the command that matches your operating system and then restart the Nessus service.

# sudo su -
# /opt/nessus/sbin/nessuscli fix --set path_to_java=/usr/bin/java
# /etc/init.d/nessusd restart

Now reload the page and Check whether you are able to Extract the PDF Report or Not.

Reference Articles

How to Install Nessus Vulnerability Assessment Tool in Linux.

Vulnerability Assessment of Linux/Unix Servers Using Nessus Tool Scan.