Batch exporting MXD to PDF files using ArcGIS Desktop?

Export Map Document to PDF is now included in the arcpy.mapping module

Pith of code sample from Esri KB How To: Export map documents to PDF using Python:

for mxd in mxd_list:

    current_mxd = arcpy.mapping.MapDocument(os.path.join(ws, mxd))
    pdf_name = mxd[:-4] + ".pdf"
    arcpy.mapping.ExportToPDF(current_mxd, pdf_name)

For a more extended Toolbox example see Export MXD to PDF courtesy of @bteranUFA