What is the best solution to print a letter in C# .NET 2.0

Question

I have a letter and label to be printed on an invoice sticker sheet.
I need the print to occur without operator intervention.
Ideally the source of the letter would in part be an RTF to allow the end user to customise the content.
Then the label hand positioned to fit into the removable label.

There are so many print interfaces, which one do the readers here recommend ?

Dave.