I would like to copy the PDF certificates to an USB drive but I cannot access the folder where KillDisk stores the certificates

This is how to retrieve PDF certificates stored on KillDisk Systems. 

• Open PCManFM-Qt File manager (Or you systems file manager)
• Choose Computer/File system destination
• Press Toll/Open as Root in Main Menu
• Enter root password (by default password is 1111)
• In context menu in file display area select Show Hidden
• Open certificates location
• Select and copy your certificates