This is a pretty vague question at this point...

When trying to print or save to a pdf I run into the following problems with "long" smath pages:

I'm not sure what the cutoff is but at some point if I print to pdf it will not work when the file is too long/large. It seems to flash a counter from 1 to 14 and stop a 14.
If I save as a pdf the file seems to be very large, although it could be due to the images in the file. When I "optimize" the pdf (via the pdf software) it usually reduces the file in half.

Are the images the issue? Or is there something else going on?

That's interesting, I'd never heard of anyone couldn't do the export because of a large size of a final document. As far as I know, the very solution could take place here is to split that file into several ones, to export and only then merge them again. And to compress this with the tool like that https://www.altocompresspdf.com/ in order to decrease its size without quality loss. And it would be able to read from other devices except desktop