Creates and returns a print operation for the document's contents.
The print settings dictionary to use.
On return, if the print operation could not be created, a pointer to an error object that encapsulates the reason it could not be created.
The print operation, or nil if unsuccessful.
The print operation can be run to print the document’s current contents. The NSPrintInfo attributes in the passed-in printSettings dictionary are added to a copy of the document’s print info, and the resulting print info is used for the operation.