If you can print them, then you should be able to install a pdf printer driver to your os and print it out as a non-encrypted pdf. You might also have a look at pdf ripping software. They also usually support converting the pdf to html, which might be ideal for you. I think that at some point I saw some programs that basically used adobe pdf reader to open pdf file, then used automation script to

take a screenshot of the pdf area on the screen
save it as png (or whatever)
move the mouse to the next page button
press the button
Then the system repeats that automatically until book is saved as a series of image files. After that, it's simple to use OCR to process the pages and get a pdf as a result (or html).