New in the SumatraPDF [pre-release builds](https://www.sumatrapdfreader.org/prerelease):

## Change Background Color

**Change Background Color** (`CmdChangeBackgroundColor`, command palette) opens a color picker to change the background color for the current file or for all files of the same type. It has swatches for saved custom colors (`CustomColors`). New settings `EBookUI.BackgroundColor`, `ComicBookUI.BackgroundColor` and `ImageUI.BackgroundColor` set the background for ebooks, comic books and images. All background color settings accept `checkered` for a transparency checkerboard.

![The Change Background Color window with custom color swatches, over a document with a light green background](https://files.sumatrapdfreader.org/assets/sumatrapdf/changelog/img/change-background-color-0369.png)

## External viewers as toolbar buttons

The `ToolbarText` option for `ExternalViewers` adds a toolbar button that opens the document in that external viewer ([#5313](https://github.com/sumatrapdfreader/sumatrapdf/issues/5313)).

![Toolbar with Acrobat and Notepad buttons added by ExternalViewers entries with ToolbarText](https://files.sumatrapdfreader.org/assets/sumatrapdf/changelog/img/external-viewer-toolbar-buttons-484a.png)

## WOFF fonts and more print copies

Documents that embed WOFF fonts display correctly ([#944](https://github.com/sumatrapdfreader/sumatrapdf/issues/944)). `-print-settings` allows up to 9999 copies ([#5509](https://github.com/sumatrapdfreader/sumatrapdf/issues/5509)). The `Scrollbars` setting moved from `FixedPageUI` to the top level.

More: [changes from April 10, 2026](https://www.sumatrapdfreader.org/docs/Changelog-2026-04-10) and the [full changelog](https://www.sumatrapdfreader.org/docs/Changelog).