Look for links which use unusual (non-alphanumeric characters). These can cause that problem.
Thanks, Steve, but it didn’t work. I looked over all - I think it is 51 links and I even removed parentheses, # and - characters which I have always used freely, but it still isn’t working. I started a new document and copied each page individually and tried to package it after every few pages. I got through page 23 of the 28 page document, but on page 24 it balked. and when I removed page 24, it till wouldn’t work. I have several things I might try as workarounds, but I know they won’t solve the basic problem - dividing the 28 page document into sections, and making my own separate file of all the links - if I don’t solve the problem within a couple of weeks, I may have to use this old-fashioned way of sending things to the printer like we did 20+ years ago. Or put it on a flash drive and drive 20 miles to hand deliver it!
Wait. This is for a printer?
Send a PDF.
This printer has worked from a pdf but they prefer to have all the fonts and links. However I finally found three jpeg pix, all from the same source, that seemed to be causing the problem. I had had no warnings opening the document or exporting it. So I put them in Photoshop and saved them as tiff files and that worked.
Thanks for helping out!