On: Computer Software (1984)

I'm new to Fermat's Library, but I'm perplexed by what they've done. They appear to have OCR'ed the paper, and it appears that you can select a region of text, but if you copy that region and paste it, it consists entirely of garbage characters. Similarly, they've somehow broken CMD+f.

Looking at the HTML source, it appears they've used pdf2htmlEX: https://github.com/coolwanglu/pdf2htmlEX / http://coolwanglu.github.io/pdf2htmlEX/ -- the first demo there (which is also from a scan) also seems to have the same property you mentioned.