If you finally decide to use images, the best choice is to employ svg tables. Sometime ago I wrote a little tutorial about how to create them:
https://www.mobileread.com/forums/sh...00#post3111300
Perfect results are obtained only if the .pdf are saved with the highest quality. I discovered that the built-in "Save as .pdf" command of the spreadshet, it doesn't make a good .pdf. It's preferable to save the sheet as .pdf with a program like pdfFactory.
Regards
Rubén