All this books was made by Underdog (Mrs. Sarinee Achavanuntakul) for site Home of the Underdogs. Site is dead long ago, and no one got extra scans to put out here. You are welcome to try, though.
Making PDF is very simple, if you need scan only. Most scanners even have build-in option "make pdf". It can be done in most editing programs and some free "pdf-printers" that will "print" your document into pdf-file. But... it will be buch of
pictures. Not editable text.
Still I would prefer it this way. It's always possible to make text from pictures, but nothing will give you good pictures if it already destroyed by text.
You need OCR program to make text from scanned image. I use Abbee FineReader (just because it's good, and moreover, my work bought it
, but you can prefer something else.
I can remove PDF protection, if it needed. PM me for that. I don't remember though if books here are OCRed. Chances are, they are not, so you wouldn't be able to edit anything right away.