I don't really know. The one built-in to the Dropbox app was perfect (but I ditched them when I moved to grapheneOS). Most of the others just dump high-res jpgs in, and that makes the files huge for just a 4-page document. The one I found (below) works great, though. 4 page document was legible enough at under 1 MB. Which reminds me, I should go zap the dev...