Hello,
Thanks for describing your issue. On our website we provide a fix to this kind of problems.
The reason of the issue that the default font (“Helvetica”) we use for generating the PDF files through PHP does not support all multi-byte characters. For this reason, we suggest “installing” (uploading some extra PHP font-files) a more robust font, like “Dejavusans”, which supports any multi-byte characters. We do not include this font by default in the plugin because it weighs like 1MB. This is nothing for the disk space of your web hosting, but for the size of our WordPress plugin this would be a quite large increase of size.
Please find the instructions on our website by visiting the section Knowledge Base – VikRentCar – Email Messages & PDF Files – Invalid Characters. There you will find the solution to upload and install the Dejavusans font files.
We hope this helps!
The VikWP Team