Ideally DWG files can be published as DWFx (which is really an XPS file – for more info please see http://autodesk.blogs.com/between_the_lines/2008/02/dwfx-and-autoca.html, http://dwf.blogs.com/beyond_the_paper/2007/02/autocad_2008_dw.html).
Besides AutoCAD, 'Autodesk Design Review' and 'TrueView' are FREE apps that will allow you to convert from DWG to DWFx/PDF.
Another option for conversion from DWG to PDF/XPS is using PDFNet Virtual Printer Driver (as shown in the Convert sample - http://www.pdftron.com/pdfnet/samplecode.html#Convert). For this to work you would need to associate dwg extension with any app (e.g. a viewer) that can print a DWG file.
Finally there are wide range of affordable third party command-line tools that could be used to convert from DWF to PDF. Some of them are:
dwgpdfconverter.com/products_dwg2pdf_features.html
dwg-converter.com/dwg2pdf/index.htm
freefirestudio.com/dwg-to-pdf.htm