That is what you think. Do you know how to use Preview on OS X ? (to still get PDF data into a copy of a part of a pdf ?)
Screen copy here have a 144dpi resolution. (both OS X and WIndows 10, <> laptops).
Some minutes after I pressed the button to send this answer, I realized why I had trouble with them !
The top answer means that I can make a copy of a pdf using Preview and the second part tells that when I make copy using Preview I get them at 144 dpi.
The first is 100% true,
the second, is I made a screen shot as meant by Michel is 100 % true too, but can be interpreted differently.
Sorry for the eventual misleading. ASk if I am not crystal clear now.