I'd use MS write as a pre-installed application reading RTF and printing to a PDF printer. Your perl just needs to control the process, maybe by using a "print to PDF" dll.

I'm working in software validation for the pharmaceutical industry, so I know that customers would highly prefer use of standard software. The development and validation effort for a perl script is much higher.

Getting into touch with the final customer might be difficult in your position, but would be worth it.