First of all, I've never posted here in this forum and haven't had Affinity for very long but I am very impressed by the community here and your kind responses! The original files are all saved in greyscale while I have been exporting in CMYK, so I'll try that, looking at the file sizes for the art I can see that they were enlarged (dpi) when I imported them and scaled them down to fit. Is there an easy fix by changing the export settings, or will I have to go back and change all the art? (there are more than 100+ illustrations)... I used all the same techniques when I created this same book in InDesign and it exported the pdf at only 62mb, clearly I don't understand the difference in them. I can't really afford to pay Adobe's exorbitant fees and there is so much I like about the way photo/publisher work together, this has been my first real stumbling block, but man I keep stumbling over it!
Thanks again for all of you help!! I'm new but learning!!