It is a much better idea to put this surplus information into a secondary download. You should offer two downloads. One with english, offering to download additional languages remotely during install, and a second tagged multilang.
Help files for many languages is a waste of time/bw for all people INCLUDING your own webserver. Hosting is not free afterall. People generally only need one language, regardless of which one they prefer. You can obviously add a few more single-language downloads as needed, For everybody else, it's easy enough to click a checkbox during install.
However there are other reasons that cause this to be a bad idea. For me, I look at the program and say... that should take up 1-2MB, I get to the download page... and then 'holy crap, its 20MB.... what did they sneak in there.' At very least, I might run it in VM before hand, others might skip it entirely.
With 20MB of space, or even the more conservative 5-10MB ... the program could potentially contain any number of malware. Granted, it does not... but the person wont know without downloading it.
Even if the user had a bit of faith (or oblivious) about malware, they might be concerned that a program that runs all the time might actually be USING 10-20M. Again, it does not... the main exe is <1.5M and running memory <6M on my pc, with all dlls etc. Though, I don't usually flinch under 100MB as long as it is a trusted application, and sounds reasonable for the type of application; others might.
Also, this is coming from someone who downloads dozens of gigabytes on a whim. People on dialup will obviously have another reason as well. A friend of mine was visiting family and was stuck with dialup for a few months. he wouldn't even take the time to download necessary things like adobe reader, or winamp because it took too long. Granted, adobe is huge (I convinced him to try foxit)... but winamp is not.
In summary... yes you could make it a hair bigger, but don't go crazy, and try to make the unneeded information modular during install (not included until needed). Also, if you do go making a huge multi-lang package... make a english only package to give some perspective to people downloading.