does anyone know if it is possible possible to trigger Conga action(generate document/send email with attachment/create attachment) from apex code - best would be trigger or batch. Example will be appreciated.
According to @CongaPete in this thread: Run Conga Composer (release 8) in background mode via HTTP Callout, you cannot do this in Conga Composer 8. Instead, you can still use the Conga 7 endpoint https://www.appextremes.com/apps/conga/pm.aspx and the same querystring parameters.
One note, you will also need to use the old Conga 7 style merge syntax, not the new Text-Based Merge Fields.
I recommend the DS7=5 parameter as well.
It is possible. You need to purchase the Conga Workflow package.
See info here: https://support.getconga.com/Conga_Composer/Conga_Workflow