Seriously what is the best pdf compressor I can get?
All PDFs are compressed with zip from memory, so you won't necessarily get better compression performance from one PDF generator than any other. You will get better or worse rendering quality, though. Many of the cheaper ones are based on ghostscript, which is (or was) proscribed from using certain dithering and other rendering optimising algorithms by patent encumberance. Historically, PDFs produced using these systems (e.g. PDFCreator) produced slightly inferior quality PDF output to Distiller for precisely that reason.
Now, if you're comfortable building it from source, many of these are available as compile-time options. As I understand, it's possible to compile in some patent encumbered stuff, although I can't remember the details of what. Also, the patents are expiring, so this situation may have improved from the 10+ years ago that I first looked into it.
However, unquestionably the best rendering quality will be obtained from Distiller (A.K.A. Acrobat Pro), which can be obtained from Adobe. I have it through owning CS6 which comes with it.
If you're concerned about size, you will probably have to tweak the graphics themselves. You can dial up or down the resolution of bitmaps - use 72 dpi or 96 dpi for screen optimised PDFs. Use vector formats where appropriate, assuming your software supports them - EPS, SVG or EMF. Separate screen and print versions let you have higher resolution graphics for print but smaller and faster versions for on-line reading.
The compression tools do this sort of thing, reducing the size of images by resampling them. They can also bin out unused characters from fonts and do various other optimisations like this. You will probably have to frig with them to see which one gives you the results you're after.