Use your browser's back button to return.

(Doing this will reload the previous page. You then may have to find (by scrolling to) the place where you were reading.)

Navigation note: Instead of clicking ( = leftclick) on an external link, you can rightclick ( = control+leftclick = two-finger click) instead. Rightclicking brings up a menu including "new tab". Clicking (leftclick) chooses this option. (Depending on your browser, you may have to click again on the now available tab title bar to open the external link in this tab.) To return to the original page, just close (X) the tab. The original page will be just as you left it, with never a need to scroll.

I recommend opening up a new tab (by right clicking) for all external links, and for internal pdf files. (These are the places where I can't insert a "return" link.)