I mean once you get into a pdf. Sometimes web page opens it instead of allowing download. The built-in pdf browser of chrome has no option to save it locally on android phone. I have not been not precise in explaining, because I find Google and Android constantly reducing my ownership of my own phone and that's another brick in the wall here

Click on the three dots top right.

There is now a bar of 5 icons at the top. The middle icon, "download", saves the PDF.

Edit: Long-pressing each icon will show you small pop-up text for the icon/action.