1. Planet eBook     Website Link: https://www.planetebook.com/

2. Free-eBooks dot net  Website Link: https://www.free-ebooks.net/engineering

3. ManyBooks   Website Link: https://manybooks.net/

4. LibriVox   Website Link: https://librivox.org/

5. Internet Archive

6. BookBub

7. Open Library   Website Link: https://openlibrary.org/

8. BookBoon  Website Link: https://bookboon.com/

9. Feedbooks

10. Smashwords

11. Project Gutenberg

12. Google Books

13. PDFBooksWorld

14. FreeTechBooks

15. Bookyards

16. GetFreeBooks

17. eBookLobby

18. FreeComputerBooks

19. OpenCulture

20. LibGen

21. Good Reads

22. Obooko

23. O'Reilly

24. Pdfdrive

25. Anna's Archive

26. Pdfroom   Website Link: https://pdfroom.com

27. Pdf Coffee   Website Link: https://pdfcoffee.com

28. Dokumen Pub

29. Z Library

30. Ocean of PDF    Website Link: https://oceanofpdf.com