pdf to kes conversion is most likely searched in the context of text-to-speech transcription using the Kurzweil 3000 software, because .kes files are the default document format from that software.
According to online documentation, PDF is among the formats supported for import for this purpose, so it shouldn't be difficult to make transcription of these documents using Kurzeweil 3000. Of course this is intended for PDFs that contain text, not graphics and least 3D graphics.
Updated: January 17, 2024