@Jellby
Thanks a lot for your precious help. One reader reported me that he could not read my EPUBs with his brand new ONYX M92. I think, this way, it is possible to offer him a 9.7 inches PDF solution without having to renounce the use of embedded fonts, dropcaps and other niceties. And for the trouble, he gets on top of this a justified text...
I'll fix these disordered apostrophes. Thank you also for spotting this.
C'est une honte.
BTW, I wonder also if the CSS kind of PDF produced with Prince could not allow the use of thin spaces? When you display a ragged text, like in common EPUBs, it may seem superfluous to bother about thin spaces. When you have a nice justified hyphenated text..., then maybe it's time to think seriously about it.