In some cases, undo could cause the PDF to be detached from background
added a zoomBehavior parameter to test some features regarding PDF rendering performances, thanks to a new application called 'Paper' (already available for a while in some Geneva schools) has been added, thanks to François Le Cléac'h.increase performances when zooming on a PDF ( enableQualityLossToIncreaseZoomPerfs enabled by default in preferences).For older operating system versions, such as macOS 10.12, Windows 7 or Ubuntu 16.04 for example, all OpenBoard releases are available on the GitHub wiki releases page, with their features.