this question has been asked in a general way before, but this is my first week with Ubuntu and I can't understand all the instructions here: How to associate a file with a program installed in wine Danne's answer was: 'Right click, Open with other application. If your application is not available in the list, use custom command and put wine ~/.wine/drive_c/Program\ Files/Yourapp/Yourapp.exe in the box.' What is 'custom command'?
I also saw the instructions at https://help.ubuntu.com/community/Wine#Creating_file_associations But the other way looks easier..
In particular I want to open pdf files with Sumatra PDF. I have Ubuntu 14.04.
Thanks for your help,