I just installed STATA 16 in my Ubuntu machine and everything is running well. However, when I need to access the help option of a command, STATA don't open the pdf documentation. When I click in "(View complete PDF manual entry)" the Ubuntu terminal prints the following message:

Code:
/usr/local/stata_pdf: 67: [[: not found
I cannot understand what this message means. How can I fix this issue and access the pdf documentation?