we have located several PDF files on local webserver. We access them via html page. With default Apache server settings the files are loaded on each back/forward button. I've found it is due to the splitting the file into smaller parts during download. If HTTP header in server setting is changed to "Header set Accept-Ranges none", files are loaded in one block and already loaded PDF file is then displayed immediately (without redownload) on back/forward buttons. But it has one strange side effect if PDF file is quite large (35MB in our case). While in MSIE everything still works fine, in Firefox we get the error message "The file is damaged and could not be repaired."