ExportToPDF() - exports the page layout or data frame of a map document to a PDF.
From Esri WebHelp:
PDF files are designed to be consistently viewable and printable across different platforms. They are commonly used for distributing documents on the Web and are becoming a standard interchange format for content delivery. ArcMap PDFs are editable in many graphics applications and retain annotation, labeling, and attribute data for map layers from the ArcMap table of contents. PDF exports from ArcMap support embedding of fonts and thus can display symbology correctly even if the user does not have ESRI fonts installed. PDF exports from ArcMap can define colors in CMYK or RGB values.
Example: Export Page Layout
ds = r"c:\temp\ds.mxd"
mxd = arcpy.mapping.MapDocument(ds)
Example: Export a Single Data Frame
mxd = arcpy.mapping.MapDocument(r"C:\temp\layout.mxd")
df = arcpy.mapping.ListDataFrames(mxd)
arcpy.mapping.ExportToPDF(mxd, r"C:\Project\Output\ProjectDataFrame.pdf", df,
You can find more information about ExportToPDF() here.