Convert into pdf format using asp .net with background image

If you mean that you want to load your image and save it as PDF format on server side, I am currently using leadtools (programming toolkit) to load the image file and save it to PDF on the same server. More information can be found here.

But if you mean that the client will load the image, and you want to save it as PDF format, you need to use a REST or WCF services on the server side, so that you can pass the image data from the client to the service, convert it to PDF, and then send the result PDF file from the service to the client to view it.