Adode Acrobat is the program of choice for educational and governmental institutions. Just choose your platform and download. The link is at the bottom of the page. Download the handbook. Right click on the book with the turning pages at the bottom of this page.
Value is extremely subjective.
This has covered the costs of a secure server, a merchant bank account, and a file transfer server. These are the people that make out, not the teachers or the students. I would have like to have sold it for much less. Download the handbook, peruse through it, and then send me a check for what it is worth to you . It cannot get any more simple than that.