Original PDF/True PDF /Print Replica /HIGH QUALITY/HQ SCANNED PDF all have Similarities to the Hard Copy & Can be printed or used in a similar manner (Table of Contents a.k.a TOC, & all other Pages are marked with numbers).
Other Scanned PDFs may be Low Quality Scanned from used or Old Books
EPUB KINDLE MOBI are all digital book Formats & cannot be printed to look like the textbook (the TOC and pages dont have numbers).
All these digital Formats can be converted to a PDF and thats why its called Converted PDF. These Converted PDFs dont have page numbers even in the Table of Contents but clicking the Contents redirects you to the exact page (Depending on your PDF Reader).
Irregardless of any format , all our ebooks come with search capability a.k.a Find in Page / OCR (in PC/MAC, CTRL + F/CMD + F ) . to help you navigate topics & with this possible you can easily convert them to audiobooks on many websites.