Compressing document with forms

Question

I have 1500 PDF documents to compress so they can easily be downloaded/sent (seperately or in small groups) via email.
- They are engineering drawings of various industrial products, hence have images on them.
- They also have fillable form fields, using Arial Bold and Arial fonts; Drop down selectino box for the title (Arial Bold); and multiple check boxes for ticking options on the products.
- The current average size ranges between 1.3 to 2.5MB, and I would like to have them below 500KB each. I know that this is possible, because our competitors have similar product sheets available on their website at that low file size.
- We do not have high res pictures, they are all low res.
- I have already tried the following (in order)
using multiple third party softwares to shrink the files, but they flattened the form submission fields, and having editability is important
Resaving all files as Reduced PDF files ( cut down around 30% of the file size)
Optimizing a few (this did absolutely nothing)
opening each file individually in "combine pdf files" section and save a single document, thus shrinking each one. (this worked better than step 2, but is extremely tedious, and is inefficient for all 1500 sheets)
Is there a way to expedite this compression, without losing fillable forms? (Low quality images is acceptable - editability of forms is important) Thanks!

Answer 1

I wanted to add some numbers, so I ran a few informal tests. I created a document with a single blank page and added 1 to 2 text fields using different fonts. Here are the results (Acrobat 9, WinXP):
Field 1
Field 2
File size
Helvetica
NA
6.09 KB
Helvetica
Helvetica Bold
6.66 KB
Arial
Helvetica Bold
209.42 KB
Arial
Arial Bold
407.58 KB
Helvetica
Helvetica Bold
407.70 KB
Arial Unicode
NA
9.14 KB
The fifth item was after switching from Arial to Helvetica and included to show that the file size doesn't decrease. Also, when using Arial Unicode it doesn't embed the entire font as I indicated earlier, so I was either entirely wrong or misremembering something else, but the font will need to be available on each user's system for it to work correctly, as with the large asian fonts used with form fields.
The numbers were roughly doubled when using Arial with Acrobat 9 and Mac OS 10.6.8, perhaps due to the difference in the size of the fonts. Other versions of Acrobat and OS will probably be different.