Adding a 3of9 barcode to a pdf

Hello. I need the ability to add a barcode to a previously generated pdf so it can be scanned and associated with a visit. We do not generate the reports so it is being added aftwards. Report length varies from 1 page to 12 and I can't always put the barcode it the same location on the page due spacing constraints. Is there a way to store a text box that I can easily copy and paste to each page as needed. Assuming I'm not the first person to want to do something like this, but searching related to pdf and barcodes brings up information on generating forms with barcodes.