The current version of drawtiming allows to generate the PDF output, but it is just encapsulated bitmap.
It makes it pretty unusable for generation of publication quality diagrams :-(.
Unfortunately the drawtiming generates the libMagick calls directly. Maybe there is a need for an emulation library, which could translate the libMagick calls into the PDF generation commands?
Maybe it should be just done by adding true PDF output into the libMagick?