好耐以前試過 scribd
開個a/c 就可以upload資料上去
咁就可以share 條link俾人下載(free download)
而家係點做就要研究下先
https://www.scribd.com/
ibooks 應該容易啲
不過就一定要有apple ID
詳情可參考
https://support.apple.com/en-ke/HT201183
Google Books麻煩少少
https://support.google.com/books/partner/checklist/4489282?hl=zh-Hant