I would like to take a single page jpg, and experiment with various pdf compression settings and other settings (to analyse resultant pdf size and quality) - can anyone point me towards decent tools to do this, and any useful docs/guides?
Adobe Acrobat Distiller, Ghostscript, possibly others. Acrobat has its own manual, Ghostscript documentation can be found at:
http://svn.ghostscript.com/ghostscript/tags/ghostscript-9.02/doc/Ps2pdf.htm
for the current version PostScript to PDF conversion (print your JPEG to a PostScript file before starting).
If your original is a JPEG, then the best quality output will be to do nothing at all to it, simply wrap it up in PDF syntax.
If you insist on downsampling the image data (which is the only way you are going to reduce the size of a JPEG image) then you would be advised not to use DCT (JPEG) compression in the PDF file, as this will introduce objectionable artefacts.
You should use a lossless compression scheme instead, eg *"Flate".
Your best bet would be to go back to an original which has not been stored as a JPEG, downsample in a decent image application and then convert to JPEG and wrap that up in a PDF.