Have you considered using proxies? Create lower resolution versions of your renders in Photo and link-place those and work on the layouts. Then when you are finished, relink (I assume you are linking instead of embedding!!!) and replace the low resolution proxies with the high resolution versions. Use the Resource Manager to accomplish this in Publisher.
Then export to PDF (if Publisher still chokes, work in smaller sections, and use a tool like PDF Exchange Editor (or Acrobat) to collate all pages).
