LyX text processor supports export to several documents format, including PostScript or PDF for printing. There doesn't seem to be any other choice for this conversion, but you can download LyX for free and it is available in versions for Windows, Linux or Mac OS X.
Convert LyX document to Adobe PostScript document.
We have found one software suitable in our database for this conversion.
Multiplatform software - convert lyx to ps on any platform
A document processor program
Convert from lyx 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.