Does this web application use an ArcGIS API (e.g. for Flex, Javascript, etc.)? - Yes, ArcGIS Javascript API
Does it use ArcGIS Server to serve the data? - Yes
When you say 'using a geoprocessing', does that mean a geoprocessing service or a tool in desktop (or a stand-alone script)?
- Geoprocessing service.
I am using ArcGIS 10.0. I know there is a Export Web Map in ArcGIS 10.1. But I could not use it right now.
A sample work flow could be: After user does a selection, the application will display the features that user selected on map. Then user can click 'Print' button to print the features and base map to a PDF file.
Thank you for any help.
Cindy