lucy24 - 1:45 am on Dec 10, 2011 (gmt 0)
You can fine-tune some things but in the end it will often down to "The problem is on your side". Not a happy resolution.
The good news: "Not very computer literate" means they are probably using whatever browser came with the computer, so you don't get the extra problems that come with having multiple browsers installed.
Concrete example: Safari has a built-in PDF reader which works nicely. But if you have plug-ins installed for other browsers, Safari will try to use them, resulting in an unreadable PDF. Unfortunately Safari doesn't let you disable individual plug-ins; it's all or nothing :(