I use GIMP 2, but it’s certainly possible its export function provides the same option.
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The RIOT plugin in IrfanView (separate download, see IrfanView plugin instructions at the IrfanView website) allows you to set a target filesize for the output image; the plugin will frob away for a little while finding the “best” quality setting which will result in an image file no larger than the stated target size. That sounds like approximately what you are asking for. It works quite well for photo images in my experience. n.b. IrfanView is scriptable in Windoze without too much grief.
For graphics which are not photographs, but which are the output of drawing/drafting tools, .EMF format (note: not, .WMF, .EMF) is usually your best bet if you can. That way you get the fewest scaling artifacts with line art, and the text re-renders (with anti-aliasing assuming TTF fonts) at the final output size and nominal resolution.
If you have Acrobat Pro (at least in version XI) there are a large number of knobs available as settings in the Save As Optimized PDF optim.
I assume you are linking all the JPEGs
If you’re on a Mac, Graphic Converter is the tool for the job.
Aside: Apple’s Preview can’t hold a birthday candle to GC, which is indispensable as far as I’m concerned.