You will suddenly realize those old Casio arrangements sound like a professional studio track. The bones are good; only the original "Tone 01 (Piano)" is dated.
Modern PDF readers and music-specific apps (like forScore, Newzik, or even standard Adobe Acrobat) allow you to write on your digital sheet music without ruining the original. You can highlight difficult passages, circle accidentals you keep missing, or write fingerings in the margins. Best of all, if you make a mistake, you can "undo" or erase it, keeping the sheet music clean for the next practice session. Casio Piano Song Book Pdf
Once you have the PDF on your iPad or printed out, try this: You will suddenly realize those old Casio arrangements