One strategy I have used succcessfully which was causing problems for online Statutory submissions with large image heavy files was as follows and may be helpful. The starting files size was 34MB - Finished File Size was 558 KB . I had tried compression both on Vectorworks Tools and Online Pdf Compression but they didn't really reduce file size by very much.
1. Screen grab the group of images from the Sheet Layer
2. Import into Paint ( or Apple equivalent) and crop only the image selection
3. Save to Project Folder
4. Import the saved image back into Vectorworks Sheet and print / export to pdf
The resulting image quality was still very legible at A3
While this may not solve large file syndrome for larger files to be worked on by others or for printing ( Dropbox / We Transfer ) may be better .
Hope this of some help as it was causing a real headache.