Enable and Disable Browser Caching with .htaccess

htaccess-cache-config

 # Enable and Disable Browser Caching with .htaccess
 
 ## Enable Examples
 
 ### 1 MONTH for static assets
 <filesMatch ".(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$">
 Header set Cache-Control "max-age=2592000, public"
 </filesMatch>
 
 ### 1 DAY for rss feeds and robots
 <filesMatch ".(xml|txt)$">
 Header set Cache-Control "max-age=86400, public, must-revalidate"
 </filesMatch>
  
 ### 4 HOURS for your real articles files
 <filesMatch ".(html|htm)$">
 Header set Cache-Control "max-age=14400, must-revalidate"
 </filesMatch>
 
 # Disable Example
 
 <filesMatch ".(html|htm|js|css|jpg|png)$">
	FileETag None
	<ifModule mod_headers.c>
		Header unset ETag
		Header set Cache-Control "max-age=0, no-cache, no-store, must-revalidate"
		Header set Pragma "no-cache"
		Header set Expires "Wed, 08 Jan 1975 05:00:00 GMT"
	</ifModule>
</filesMatch>

# Tips on Usage:

-- .htaccess configuration effects the directory contents in which it resides, as well as its subdirectories
-- .htaccess cannot be ready by browsers so it is secure for other operations.
-- creating the .htaccess file is best done on the server because most OS system settings will initially hide any file created that begins with a "."

If a browser has already downloaded a file - like a PDF - and the above is added to the htaccess file after the fact - is there any way to force future downloads of the PDF to fetch the new version of the PDF vs the one downloaded originally? I've tried the above and other no-cache htaccess snippets but every time the old PDF is downloaded. Is the only solution (other than renaming the PDF or adding a unique query string parameter) for the end-user to clear their cache?

@cemerson yes just add random string on end of download url
mydownload.url?cache=RANDOMHERE