Sending URL link for PDF to users defined by filename

I have unique uploaded pdf files on our server where the filenames are the LINE ID of various users ( I achieve this by using a barcode on the scanned document that changes the filename of the PDF to the LINE ID data found in the barcode). Now I need to find a way to send the URL for each PDF to the relevant user by using the filename in a variable parameter in a Push Message using the LINE API. Would really appreciate any ideas or help with this.