[issue] wkhtmltopdf

Example:

  wkhtmltopdf http://google.com google.pdf

qt.qpa.screen: QXcbConnection: Could not connect to display
Could not connect to any X display.

 odoo@Odoo-Server-PC:~$ export DISPLAY=':0.0'

libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
Loading page (1/2)
Printing pages (2/2)                                              
Warning: Received createRequest signal on a disposed ResourceObject's NetworkAccessManager. This might be an indication of an iframe taking too long to load.
Done         

Or
You can remove and install diffent release.