This text is almost unreadable to me. The characters are actually touching one another, blending together.
If anyone wants more punishment, the rest of the document is here: https://ista.org/docs/1Aoverview.pdf
Also, relevant xkcd: https://xkcd.com/1015/
It looks like a font substitution issue. You don’t have the type face installed that was originally used to create this PDF. And the font was not embedded in the PDF. So whatever you’re using to view, the PDF is utilizing something like Aerial or Helvetica as a stand in sans serif type face but retaining the kerning/layout used for the original font.
Can confirm it is a font substitution issue. When I open the PDF a different font is used (note the very distinctive “r”) which has much better (but not great) kerning.
It’s better, but still horrible in its own special way.