Persisted data is stored in SumatraPDF-settings.txt file.

In portable version the file is stored in the same directory as SumatraPDF executable. In non-portable version, it’s in %LOCALAPPDATA%\SumatraPDF directory.

Starting with version 1.6 we also persist thumbnails for “Frequently read” list. They are stored in subdirectory sumatrapdfcache as .png files.

See https://www.sumatrapdfreader.org/settings/settings for information about all the settings.