For efficiency, DocView caches the images produced by gs.
The name of this directory is given by the variable
doc-view-cache-directory. You can clear the cache directory by
typing M-x doc-view-clear-cache.
To force a reconversion of the currently viewed document, type
r or g (revert-buffer). To kill the converter
process associated with the current buffer, type K
(doc-view-kill-proc). The command k
(doc-view-kill-proc-and-buffer) kills the converter process and
the DocView buffer.
The zoom commands + (doc-view-enlarge) and -
(doc-view-shrink) need to reconvert the document at the new
size. The current page is converted first.