To screenshot an entire page, first make sure make sure your phone has the iOS 13 update and that you're using Safari rather than another browser or app. Second, screenshot the page like you usually would, holding down the upper volume button and the button on the opposite side. Third, click the screenshotted image that pops up on the bottom left-hand corner of your phone, then click "Full Page" at the top. Next, use the scroll bar on the right to scroll for as long as you want the screenshot to be. Once you've done that, click "Done" and "Save PDF to Files." Last, open your Files app, and you'll find the entire screenshot with your other recent files. How cool is that?!