Yes, it can be done. If you wish to develop this functionality yourself, you need to get the developer (or advanced) edition of Crystal and use the runtime components.
There are also several 3rd-party report managers (see list at:
including my Visual CUT software, that can accept a command line call from another application (asp.net, PHP, ColdFusion, ...) and undertake the requested operation for you.
The things you should be looking for are the ability to accept command line arguments (rpt file path & name, parameters, user id, password) and generate not only the exported file but also status indicators for success/failure so your application knows when processing is completed (it's time to redirect the user to the resulting pdf file), etc.
hth,
- Ido
CUT, Visual CUT, and DataLink Viewer:
view, e-mail, export, burst, distribute, and schedule Crystal Reports.