doc-view-image-width

doc-view-image-width is a variable defined in `doc-view.el'.
Its value is

850

Documentation:
Default image width.
Has only an effect if `doc-view-scale-internally' is non-nil and support for
scaling is compiled into emacs.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.