[Koha] Problem with printing barcodes

Hello, I am new to KOHA, using it in a very small rural school (valentineisd.com) in the high desert mountains of Southwest Texas, USA. I have a problem with printing barcodes and need some help please. I cannot get the call number to print on the barcodes and many times when I go to print the barcodes I export to a pdf file and then when I try to open it the following comment is made "there was an error opening this document. The file is damaged and could not be reapired." I have tried running barcodes on three different computers and three different printers and I get the same results. Any ideas as to what I am doing wrong in both of these cases? Thank you in advance. Margaret Matthews mamatthews@hughes.net Valentine ISD