Following a brief exchange of thoughts with Carlo (one of the web thought readers), I have decided to publish a list of resources aimed to the creation of Barcodes. Originally, Carlo wanted to insert a barcode in a PDF document using FPDF, however the subroutine he found generates a HTML table that is almost impossible to embed in a PDF with FPDF.
Other solution are possible. The point is to create a Barcode image, save it on the server, and then insert it into the PDF. I haven't explored the above idea, but I think that the following resources might help some to accomplish the task.
Here's the list:
Barcode Coder (jQuery)
Pure ASP Barcode Generator (pure ASP)
ASP Barcode Script (pure ASP - Thanks to Carlo)