Linked images and exporting for print

Can't say that I've ever imported images as linked but let's say I do, when I go to export for print will all be good or do I need to re-import the orig then export out?

I've been given garbage pdf's that are rather large both dimensionally, as well as, file size. I'm having to open each in photoshop/flatten/save as tif @ 150dpi. Now when go to set them up within cd for proofing as "unlinked" the file will be something like 800MB. If I link the images it will significantly reduce the file size but not sure about the print quality.

Thoughts?