The PDF of the blue regs I have is scanned. Obviously there are limits on resolution, but otherwise what you see and read is identical to the hard copy (which I also have).
It also has a hidden layer of text beneath each page image, which only becomes visible when you highlight text by click and drag. This must have been generated by some character recognition software, and for most of the time it is identical to the image text, but there is the occasional incorrect character, extra space, or character that simply isn't recognised, eg. the delta symbol.
When you use the search facility to search for a specific word, it searches the hidden text, so occasionally it fails to find something that it should have, as above, but most of the time it finds what you want. Also, it highlights the image, rather than than displaying the hidden text beneath, so you read it as it should be.
I use the pdf version all the time, it is so, so much better. The hard copy sits in a bag in my van and has probably been used half a dozen times at most.