The following Apex method can be used create a new document via custom coding. Please be aware this method requires knowledge of Force.com best practices and as always we suggest testing your code in the Sandbox.

Syntax:
AssignmentRulesService.processRule(
@ruleId,
@listOfRecordIds
);

 

Parameters:
@ruleId 
Required. The Assignment Rule Set Id to be used for processing the source record for predefined assignment actions.

@listOfRecordIds
Required. The list of Id value of the base object's source records for which Assignment Rule Set should be processed for.

Result:
The function call will return a JSON formatted string in this format: {success:"",result:""}

success
Will be either TRUE or FALSE

result
A confirmation text of completion OR error text if the process is halted by an unexpected error.

Example:
AssignmentRulesService.processRule(
   'a0b9000000RJhKT',
   new list<Id> {'a0d9000000GTrsg', 'a0d9000000GTrqa'}
);