Is there a portable scanner connect to an android phone? I dont know whether my question is right to ask here. please advise me if I need to ask this kind of question at other areas.

I am investigating to find a right portable scanner to connect with an Android mobile phone (such as HTC Desire). After scanning a paper from a portable scanner, the mobile phone will receive the file as a pdf or jpg. That's it!

Would this be possible to do?

Thanks in advance.
Try to look for Bluetooth scanners. Android supports bluetooth and there is SDK API for it so you could create your own app to receive and process data from scanner.

One such device I could find: http://www.planon.com/products/docupen/xseries