See also Installation for an overview of the portable and installer versions.

If you’re reading this, you might have been told by SumatraPDF that you have a corrupted installation.

SumatraPDF comes in two flavors: a portable version and an installer.

A portable version is a self-contained executable and cannot be corrupted.

An installer needs to be run to be properly installed. Part of it is extracting the engine library (libsumatrapdf.dll from 3.7; through 3.6 it was named libmupdf.dll).

There are two possible problems:

If you want to place SumatraPDF in any location, under any name, use the self-contained portable flavor.

If you want to use the installable version, install it. The installer will run if the .exe filename contains -install (as it will if you download an official build).

If you rename the .exe, you can force it to run as the installer with the -install option.

Alternatively, you can extract libsumatrapdf.dll and all other files with the -x option.