I've seen this done two ways. On the desktop, a German customer of mine had a very ugly SAP payroll report. They wanted to email this to staff each month, but chose to format it first using Word. I built the model to get the data from the report into a CSV file, then they used a free or cheap utility to mail merge this into Word and send the files to staff by email for personal printing.
Another approach is to format the data nicely using XSLT and to render it in a browser in Datawatch|ES, so the users can log in and pull the data down to them, rather than having it pushed at them.
You can do a lot in Monarch using a summary export split on key values, but designing a summary to format nicely with address style data can be a bit fiddly. Does your final output have paragraphs of text in or is it all data?
Olly, thanks for the input. It has got me thinking. We are implementing ES this fall. The letter is your basic coporate leader using the standard format of address block, greeting, body with 2 paragrahs and then the salutation. I did start to play with creating fields to include each bit of text line in the letter with the thought of concatenating when necessary for name, account number etc. It was labor intensive so I quickly decided to stick to the current method of pushing the key data out and letting the end user mail merge. It was a curious adventure and just thought I would ask. Bottom line, it can be done.