Acrobat lying about file size

Question

I am trying to create a small PDF using Acrobat 8 on a Mac. I have several jpg files, and together they are exactly 10.17 MB. I am using the Combine Files feature of Acrobat. I press add files, select my jpgs, and choose 'Default File Size'. I press Next, than Create. Acrobat then proceeds to combine the files, and informs that the Original Total Size is 10.17 MB, and that the final PDF size is 103.16 KB. So I press 'Save', and save the PDF file. But the PDF file that is saved is about 10.4 MB!!
There is obviously an issue here, and I'm pulling my hair out trying to figure out why the Combine Files dialog is lying to me. Please help!

Answer 1

This does not seem to help There are no embedded fonts; I'm just putting images together using Combine Files. I set the options to the following in the PDF Optimizer, and the file size is still 10.4 MB (text in red is what is selected):
Make compatible with: Acrobat 8.0 and Later
[checked] Images -
Color Images:
Downsample: Bicubic Downsampling to 72 pixels/inch. For images above 72 pixels/inch
Compression: JPEG  Quality: Medium
Grayscale Images:
Downsample: Bicubic Downsampling to 72 pixels/inch. For images above 72 pixels/inch
Compression: JPEG  Quality: Medium
Monochrome Images:
Downsample: Bicubic Downsampling to 72 pixels/inch. For images above 72 pixels/inch
Compression: CCITT Group 4
[checked] Fonts -
<there are no fonts embedded in the unoptimized PDF>
[unchecked] Transparency -
<transparency options are disabled, because it is unchecked>
[checked] Discard Objects -
[unchecked] Discard all form submission, import and reset actions
[unchecked] Flatten form fields
[unchecked] Discard all JavaScript actions
[checked] Discard all alternate images
[unchecked] Discard embedded page thumbnails
[unchecked] Discard document tags
[unchecked] Convert smooth lines to curves
[unchecked] Detect and merge image fragments
[unchecked] Discard embedded print settings
[unchecked] Discard embedded search index
[unchecked] Discard bookmarks
[checked] Discard User Data -
[unchecked] Discard all comments, forms and multimedia
[unchecked] Discard document information and metadata
[unchecked] Discard all object data
[unchecked] Discard file attachments
[unchecked] Discard external cross references
[unchecked] Discard private data of other applications
[unchecked] Discard hidden layer content and flatten visible layers
[checked] Clean Up -
Object compression options: Compress document structure
[checked] Use Flate to encode streams that are not encoded
[checked] In streams that use LZW encoding, use Flate instead
[checked] Remove invalid bookmarks
[checked] Remove invalid links
[unchecked] Remove unreferenced named destinations
[checked] Optimize the PDF for fast web view
Like I said, the above options yield a pdf of the same size (10.4 MB). I don't know what the deal is.
Recently I've had to reinstall CS3 due to a hard drive failure. Could there possibly be some default option that is different now? Because, before the reinstall I used Combined Files and it always yielded a pdf of the size that Combine Files said it would be.
Just in case additional details are needed: I'm using Acrobat 8 Professional as part of CS3 Design Standard, on an Intel Mac running Mac OS 10.5.7.