I have a DNN 5.1 site using Open Document Library (most recent version).  Many of the PDF files that I upload to the site get corrupted on the down load.  Here's a case that is TYPICAL:
1.  File X.pdf is fine prior to upload using Open Document Library
2.  File X.pdf is fine when downloaded directly from the ISP using my control panel (obviously outside of the DNN framework)
3.  File X.pdf is corrupted when downloaded using Open Document Library.

The corruption comes in the form of a bunch of XML (or HTML) added to the end of the file.  This can be seen when comparing all 3 files opened in WordPad.

These files are not large - 150kb.

I changed my web.config to look like this

<httpRuntime useFullyQualifiedRedirectUrl="true" maxRequestLength="51200"requestLengthDiskThreshold="51200" executionTimeout="1200"/> 

The problem sitll persists.
I've cleaned out the browser cache, tried it on different machines with different logins different browsers (IE7, IE8, Firefox, Chrome) and the problem is the same.

It's not user dependent, requesting machine dependent, browser dependent or produced by Adobe Acrobat 9.

Does anyone have a suggestion?

I found a solution: 

First, open Internet Explorer and got to tools> internet options >advacned then uncheck use http1. Now close IE, then open IE and test you r download. If you can download the pdf ok, then it is because IIS is compressing the files.

ok so go back in and check the boxes in IE and check the boxes so that it breaks the pdfs again.

Now go to IIS configuration - go to the yellow folder "web sites" and click properties. go to the services tab. uncheck the compress application files. (you might also uncheck the static files) . apply that and restart IIS. now test

hope this helps all you head bangers out there.