@Honey Muir 

I presume that you are on a paid/Education plan. Which plan type are you exporting from - Team, Consultant, Business, Enterprise, or Education?

The image quality is just not there

Can you provide example screenshots - one of an image that “is there” and another that is “not there”?

the words are not legible.

Can you provide screenshots - one of text that is “legible” and another that is “not legible”?

@Honey Muir - I did note this in the Board Export → Save as PDF Help Center article:

Perhaps “not legible” is also a side effect of an exported large board.

@Honey Muir - What happens if you only export one of the problem frames and not the entire board - do you still experience the issues that you have described?