What version of Web Help Desk are you using?
This may help you if you are using version 12.2: Enable full unicode support in ticket and billing PDF reports on Windows and Linux systems - SolarWinds Worldwide, LLC. …
If you are not using vesion 12.2 you can try this: Use Unicode characters in the PDF files generated by Web Help Desk - SolarWinds Worldwide, LLC. Help and Support
I was wondering if Gus's reply helped with this problem?