@BC31 on iPad specifically I’ve found that if you tap the 3-dot menu and select “Markup”, you can then download the PDF as one of the options. The alternative (which also works in many other apps) is to select Print. When the preview pane opens, 2-finger pinch outwards on the thumbnail and it will open full screen. From there you can save the PDF.

@MaxPandini I am having the same issue. Opera for iOS 5.1.0 built-in Help states to go to Settings, scroll to Synchronization, and log in. Only problem is there’s no Synchronization option! Seems they got their cart in front of their horse on this one. A major drawback to using Opera across platforms (not an issue in Safari, Edge, or Chrome…)