This has been frustrating me for a while. While Preview is an awesome bundled tool and all, it seems to think it is acceptable to create HUGE PDF files.
In order to not be hated by my EMail recipients, (see this comic strip: http://theoatmeal.com/comics/email), I tried to make the file size smaller. Here's what I tried and failed.
Also; Being the stubborn ass that I am, I wanted to do this without installing any extra tools.
My Original Size: 7 Pages of typed letter (i.e. a signed NDA agreement) at 3.8Mb (Ridiculous)
Open PDF in preview, click on File->Save As, Select 'PDF' and Quartz Filter=Black and White.
Fail: The size reduced to 594kb, but most of the text was faded out or missing. Not good.
Same as above; Open PDF in preview, click on File->Save As, Select 'PDF' but this time Quartz Filter=Reduce File Size.
Fail: Size was amazingly 217kb, but nothing could actually be read since the text had been totally blurred out. Not acceptable.
Same as above; Open PDF in preview, click on File->Save As, Select 'PDF' but this time Quartz Filter=Grey Tone.
Fail: Size was a whopping 15Mb.
Things were starting to get annoying.
So here's what finally solved it. Which is not pretty by any means.
1. Export each and every page in the PDF to JPEG format one by one.
2. For each new JPEG file, click on Save As->JPEG, then set the quality nearer to the 'Least' setting on the slide. Mine made each file about 100kb each.
3. Recreate the PDF by opening the first JPEG file in the series in Preview, then clicking View->Sidebar-Show Sidebar. Then drag and drop each of the JPEG files into the sidebar in order.
4. Select all the images in the Sidebar and then click on File->Print Selected Images.
5. Click on PDF-Save as PDF to create your new file.
My final file was 700kb and just as readable as the original.
Finally a win. Albeit a pyrrhic win.
For more about manipulating PDF files, try these following posts:
Free and Fast Way to Accurately Convert PDFs to Excel Files
Printing to PDF with doPDF
Concatenating PDFs with Ghostscript