This conversion mostly represents attempts to export PDF documents to HPGL format for printing on plotters. This is perhaps possible using some of the vector based graphics software or some kind of translation software for printing formats. You can try the open source Inkscape as it should be capable of pdf to hpgl conversion.
Convert Adobe Portable document format to Hewlett Packard Graphics Language plot file.
We found one software available in the database for this conversion.
Multiplatform software - convert pdf to hpgl on any platform
A vector graphics editor
Convert from pdf file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.