Bar Codes unreadable after conversion from Word to PDF

Can anyone explain why bar codes are not readable (if they convert at all), by a bar code scanner, after being converted from Microsoft Word to PDF? I use Wasp FontWare with Word 2003 with Wasp Bar Code 5.1.0 add-in. I can print directly from Word and the bar codes work fine, but if I print the PDF copy, the bar codes are no recognized by Symbol Technologies scanners. The latest version of PDFCreator (1.2.3) does not even import the bar codes...only blank space where the bar code should be. I believe that my old Adobe Acrobat 4.0 used to handle bar codes OK. Does anyone have any ideas on what to try to resolve this issue?