doc-view-scale-internally

doc-view-scale-internally is a variable defined in `doc-view.el'.
Its value is

t

Documentation:
Whether we should try to rescale images ourselves.
If nil, the document is re-rendered every time the scaling factor is modified.
This only has an effect if the image libraries linked with Emacs support
scaling.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.