Answer
Foxit PDF Editor provides below two types of display when opening PDFs.
1. Open files in multiple windows
2. Open files in single window
How to do
Here are some ways to set the display as an actual requirement.
1. Function setting in preferences within Foxit PDF Editor.
Please go to File tab in Foxit PDF Editor> Preferences > Documents > check "Allow Multiple Instances" , "Always open files in a new window" or "always open files in a new window/in a new instance", click on OK button to enable single document interface mode in Foxit PDF Editor/Reader. This setting will enable Foxit PDF Editor/Reader to create a new separate window when double-click to open a PDF file.
Note: Starting from version 13.0 and version 2023.2, the option “Open in multiple instances” has been updated to “Always open files in a new window".
Beginning with version 14.0 and version 2025.2, users can choose between “Open in multiple instances” and “Always open files in a new window” through the updated option "Always open files in a new window or in a new instance." This provides flexibility for users to decide their preferred behavior when opening files.
New window: Open each file in a new window (within the same application process).
New instance: Open each file in a fully separate application instance (independent process).
2. Set in registry Editor
Navigate to \HKEY_CURRENT_USER\SOFTWARE\Foxit Software\Foxit PDF Editor xx.0\Preferences \Documents\bMultiInstance
or
HKEY_CURRENT_USER\SOFTWARE\Foxit Software\Foxit PDF Editor\Continuous\Preferences\Documents
Note: Value 0 : disable multiple windows ;
Value 1 : enable multiple windows. (that is to say, always open files in a new windows)
Value 2: Enable multiple instances. (that is to say, always open files in a new instance)
Note: Setting this value to 2 is effective only for Version 2025.2, V14.0, and higher versions.
3. Set via Foxit GPO template
For perpetual licensed version versions 14.0, subscription licensed version 2025.2, and greater versions, please navigate to Preferences > Multiple Windows
For perpetual licensed version versions 13.0, subscription licensed version 2023.2, and greater versions, please navigate to Preferences > Multiple Windows
For versions lower than version 13 and Version 2023.2,please navigate to Preferences > Multiple Instances
4.Set via Foxit Customization Wizard tool
Starting from Foxit PDF Editor V14.0 and Foxit PDF Editor V2025.2 or later versions, users can configure the option to always open files in a new window or instance in the Foxit Customization Wizard Tool. as shown in the image below.
5. Set via Foxit XML Editor
Starting from Foxit PDF Editor V14.0 and Foxit PDF Editor V2025.2 or later versions, users can configure the option to always open files in a new window or instance in the Foxit XML Editor Tool, as shown in the image below.