How is the barcode reader connectected to a computer?
If it uses a common interface, like serial, or parallel, then you can definitely connect it to the PIC. If it uses USB, it's a little more difficult, but still possible.
If the barcode reader actually needs an adapter card to be installed in the computer, then you will have to pretty much emulate that card. This can be a more complicated thing, but it does not mean it cannot be done.
Can you provide more info? A link?