Use SmallPDF or ILovePDF to compress the file to "e-book" quality. A full 48-page Musigatto book should be between 15 MB and 25 MB.
Some Italian music schools use the MyLibrary app. If you purchase a new physical book, it sometimes includes a digital code sticker. You can redeem this code to download the official PDF to your phone or tablet. This satisfies the "portable" requirement legally. musigatto primo livello pdf portable download
Upload the final PDF to Google Drive, Dropbox, or Apple iCloud. Download it to your iPad, Kindle Fire, or Android tablet. Now you have a legal portable copy for personal use. Use SmallPDF or ILovePDF to compress the file