There might be another problem.
I have found that the Google PDF Viewer
does not display all pdf files properly or that when a user saves a pdf file from the viewer that it cannot be viewed using the Adobe PDF Reader
becuase it shows it has been corrupted.
If you test that you can read the pdf file on your system using Adobe Reader and that it works correctly then you should use the file naming scheme that webgift has mentioned. Then try to use it through your website as a link without the Google Viewer to see if that works.
No spaces in the filename. Please see http://wiki.elxis.org/wiki/Pdf