I know there are functionalities in many multi-functional printers that can read these barcodes and give them e.g. the name of the barcode. They will also let you process this e.g. in the document filename and put it somewhere on the server. This is also a solution where you typically have some volume and then it matters to call help of companies of multi-functionals. (like Canon, Sharp, Ricoh, ...)

In OpenERP, with the document modules, your lead documents can be accessed in a special map on the ftp/webdav server. I presume that from this barcode you can find back the lead. So, you could do an XML-RPC request e.g. in a script that then moves the file to the right folder.

You can have a networked scanner deposit the scanned images into a directory on your openERP server.

http://code.google.com/p/ocropus/

OCROPUS can be installed on your machine and will convert tiff / pdfs into text depending on the quality of the scanned image.

http://code.google.com/p/zxing/ Allows you to OCR barcodes.

Those tools will let you get the information off the document, getting it into openERP is going to require a customer module and LOTS of programming. If this seems overwhelming to you, I would get a consultant, there are lots of openERP partners.