Open the PDF, go to the page, then save or print a picture straight from it. The PDF stays on this phone.
Tap ✂ Select area, then drag over the map. Drag a corner to adjust it, or the middle to move it. Clip with nothing selected takes the whole page.
To pick the folder each time: Chrome ⋮ → Settings → Downloads → turn on “Ask where to save files”. Or tap Share and choose Files.