Consider professional tenor Lawrence Brownlee. In interviews, he discusses how he uses digital PDFs for bel canto roles. For "Chacun le sait," he loads a PDF into an app that allows him to change the contrast of the page. Old French scores have grey, dirty backgrounds that cause eye fatigue during two-hour practice sessions. A "better" PDF has a white background and black, crisp notes.
Furthermore, the infamous nine high Cs require specific breath preparation. With a PDF, Brownlee can insert a "breath mark" (+) that flashes red 0.5 seconds before the note arrives. No piece of paper can do that.
A significant flaw in standard piano-vocal scores is the lack of phonetic help. A better PDF for "Chacun le sait" includes a third staff or margin notes with the International Phonetic Alphabet (IPA). chacun le sait pdf better
For example, the line: "Chacun le sait, chacun le dit" becomes a muddle if you don't speak French. A superior PDF links to pop-up annotations (in apps like forScore or MobileSheets) showing: [ʃa.kœ̃ lə sɛ, ʃa.kœ̃ lə di].
Without a digital PDF, you are guessing. With a better one, you are learning. Consider professional tenor Lawrence Brownlee
Not all PDFs are created equal. If you search Google for "chacun le sait pdf" you will likely find the old Schirmer edition scanned in black and white. That is the "worse" version.
To find better, look for:
Pro Tip: Search for "Chacun le sait piano vocal score high resolution" instead of just the short keyword. Quality files often are hosted on university opera department websites or specialized sheet music libraries (like Nkoda or Sheet Music Direct).