Go "internet options" => "browsing history" => "Delete..." => tick everything and delete.
then go back and try to download it, that might work for you.
Uhh... browsing history doesn't have much to do with loading new pages.
If it's a browser related issue like you're thinking it is, it'd be much more likely to be an issue with the cache.
My suspicions would lie with whatever PDF reader/plugin he is using.
Yes, in case you haven't noticed.
in current version of IE, browsing history contains cache(temp files) and cookies ETC.
I just cbf telling which ones to tick since it wouldn't make much difference for him
Recommending someone to unnecessarily delete browsing history and cookies, just because you 'cbf' probably isn't a good idea. They (or someone else who uses the computer) might prefer to have that browsing history and other data for whatever reason.
On another note, it's time for you to switch to a better browser...
This is getting extremely irrelevant and off-topic, I'm going to stop discussing this now.